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Reference Manual
for
Database Systems Lab
School of Computing Science and Engineering
Vellore-632014,Tamil Nadu
Database Systems Lab Manual
CONTENTS
SNo
Topics
Page Number
1.
BASIC SQL COMMANDS
1
2.
CONSTRAINTS
13
3.
OPERATORS IN SQL*PLUS
18
4.
FUNCTIONS:SINGLE ROW AND GROUP FUNCTIONS
23
5.
JOINS
34
6.
VIEWS
45
7.
PL/SQL
50
8.
PL/SQL BLOCK SYNTAX AND GUIDELINES
58
9
CONTROL STRUCTURES IN PL/SQL
67
10
CURSORS
73
11
EXCEPTIONS
80
12
PL/SQL BLOCK TYPES:Anonymous blocks and Subprograms
85
13
PACKAGES
93
14
TRIGGERS
98
Database Systems Lab Manual
SQL STATEMENTS
SQL statements are classified as follows:
Data Retrieval Statement:
SELECT is the data extracting statement which retrieves the data from the database.
Data Manipulation Language (DML):
This language constitutes the statements that are used to manipulate with the data. It has three commands, which are INSERT, UPDATE and DELETE.
Data Definition Language (DDL):
This is the language used to define the structure of the tables. It sets up, changes, and removes data structures from the tables. It uses 5 commands, which are CREATE, ALTER, DROP, RENAME and TRUNCATE.
Data Transaction Language (DTL):
This is the language used to do undo and redo the transaction performed in the database. The commands are Commit, Rollback, and Save Point
Data Control Language:
This language is used to sanction the rights to the users to use the other user’s database objects. The commands are Grant and Revoke
Consider the following schema based on which the example queries are discussed in this manual.
BASE SCHEMA
EMPLOYEE
Name Type
-------------------------- ----------------------
EMPLOYEE_ID NUMBER(3)
FIRST_NAME VARCHAR2(10)
LAST_NAME VARCHAR2(10)
MGR NUMBER(4)
HIRE_DATE DATE
JOB_ID VARCHAR2(10)
SALARY NUMBER(10)
Database Systems Lab Manual
COMMISION NUMBER(8)
DEPTNO NUMBER(2)
DEPARTMENT
Name Type
--------------- -----------------
DEPTNO NUMBER(2)
DNAME VARCHAR2(14)
LOC VARCHAR2(13)
BONUS
Name Type
---------------- -------------------
ENAME VARCHAR2(10)
JOB VARCHAR2(9)
SAL NUMBER(10,2)
COMM NUMBER(10)
JOBGRADE
Name Type
----------------- ---------------------
JOB_ID VARCHAR2(10)
GRADE NUMBER
LOSAL NUMBER
HISAL NUMBER
DATA TYPES IN ORACLE:
Data Type
Description
VARCHAR2(size)
Variable-length character data
CHAR(size)
Fixed-length character data
NUMBER(p,s)
Variable-length numeric data
DATE
Date and time values
LONG
Variable-length character data up to 2 gigabytes
CLOB
Character data up to 4 gigabytes
RAW and LONG RAW
Raw binary data
Database Systems Lab Manual
BLOB
Binary data up to 4 gigabytes
BFILE
Binary data stored in an external file; up to 4 gigabytes
ROWID
A 64 base number system representing the unique address of a row in its table
ORACLE 9I TABLE STRUCTURES
 Table can be created at any time
 No need to specify the size of table, the size is ultimately defined by the amount of space allocated to the database as a whole.
 Tables can have up to 1000 columns
NAMING RULES
Table names and Column names
 Must begin with a letter
 Must be 1-30 characters long
 Must contain only A-Z,a-z,0-9,_,$,#
 Must not duplicate the name of another object owned by the same user
 Must not be a reserved word
Data Definition Language (DDL)
The following are the DDL Commands:
1. Create 2. Alter 3. Drop 4. Truncate 5. Rename
1. a. Creating a table
Syntax:
Create table <Table Name>
( <Field1> <Data Type> <(width) <constraints> ,
<Field2> <Data Type> <(width)> <constraints>,
..................................);
Database Systems Lab Manual
Example:
SQL> create table employee
( employee_id number(3),
first_name varchar2(10),
last_name varchar2(10),
mgr number(4),
hire_date date,
job_id varchar2(10),
salary number(10),
commision number(8),
deptno number(2));
Output:
Table created.
Example:
SQL> create table department
(deptno number(2),
dname varchar(14),
loc varchar(13));
Output:
Table created.
Note:
Other tables can be created in the similar way.
b. To view the Structure of the table, desc command is used
Database Systems Lab Manual
SQL> desc employee;
Name Null? Type
-------------------------------------- -------- ---------------
EMPLOYEE_ID NUMBER(3)
FIRST_NAME VARCHAR2(10)
LAST_NAME VARCHAR2(10)
MGR NUMBER(4)
HIRE_DATE DATE
JOB_ID VARCHAR2(10)
SALARY NUMBER(10)
COMMISION NUMBER(8)
DEPTNO NUMBER(2)
2. Alter Table Statement:
Alter command is used to perform the following action on the table:
a. Adding column in the existing table
b. Increasing and decreasing the column size and changing data types
c. Dropping column
d. Renaming the column
e. Adding and dropping constraints to the table( discussed in constraints topics)
f. Enabling & disabling constraints in the table( discussed in constraints topics)
a. To Add a column to the table (structure)
Add option is used to add a new column
Syntax:
Alter Table <Table-Name> Add <Field Name> <Type> (width);
Example:
SQL> alter table employee add address varchar2 (20);
Output:
Table altered.
b. To Modify a field of the table
 Increase the width or precision of numeric column
Database Systems Lab Manual
 Increase the width of numeric or character columns
 Decrease the width of the column only if the column contains only null values or if the table has no rows
 Change the data type only if the column contains null values
Syntax:
Alter Table <tablename> MODIFY ( <column name > < newdatatype>);
Example:
SQL> alter table employee modify address varchar2 (10);
Output:
Table altered.
c. To Drop a field of the table
Drop option is used to delete a column or remove a constraint
Syntax:
Alter Table <tablename> DROP COLUMN < column name>;
Example:
SQL> alter table employee drop column address;
Output:
Table altered.
d.To rename a column
Syntax:
ALTER TABLE <tablename> RENAME COLUMN <oldcolumnname> TO
<newcolumn name>
Example:
SQL> alter table employee rename column mgr to manager;
Output:
Table altered.
 To Drop a table - Deletes a Table along with all contents
Syntax:
Drop Table <Table-Name>;
Database Systems Lab Manual
Example:
Drop Table Student_table;
Output:
Table Dropped
 To Truncate a table - Deletes all rows from a table ,retaining its structure
Syntax: Truncate Table <tablename>
Example:
SQL> truncate table employee;
Output:
Table truncated.
g. To rename a table- Renames a table with new name
Syntax:
Rename <oldtablename> To <newtablename>
Example:
SQL> rename employee to emp;
Output:
Table renamed
Data manipulation Language (DML)
The following are the DML Commands: 1. Insert 2. Delete 3. Update 4. Select
Insert command is used to load data into the table.
a. Inserting values from user
Syntax:
Insert into <tablename> values ( val1,val2 …);
Example:
SQL> insert into department values(10,'accounts','chennai');
Output:
1 row created.
Database Systems Lab Manual
b. Inserting values for the specific columns in the table
Syntax:
Insert Into <Table-Name> (Fieldname1, Fieldname2, Fieldname3,..) Values (value1, value2, value3,..);
Example:
SQL> insert into department (deptno,dname)values(20,'finance');
Output:
1 row created.
c. Inserting interactively(Inserting ,ultiple rows by using single insert command)
Syntax:
Insert Into <tablename> Values( &<column name1> , &<column name2> …);
Example:
SQL> insert into employee values(&empid,'&fn','&ln',&mgr,'&hdate','&job',&sal,
&comm,&dept);
Enter value for empid: 111
Enter value for fn: Smith
Enter value for ln: Ford
Enter value for mgr: 222
Enter value for hdate: 21-jul-2010
Enter value for job: J1
Enter value for sal: 30000
Enter value for comm: 0.1
Enter value for dept: 10
old 2: &comm,&dept)
new 2: 0.1,10)
Output:
1 row created.
Note: Column names of character and date type should be included with in single quotation.
 Inserting null values
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Syntax:
Insert Into <tablename> Values ( val1,’ ‘,’ ‘,val4);
Example:
insert into department values( ‘101’,’’,chennai);
Output:
1 row created.
2. To Delete rows from a table
Syntax:
Delete from <table name> [where <condition>];
Example:
a) to delete all rows:
SQL> delete from department;
Output:
89 rows deleted.
b) conditional deletion:
SQL> delete from department where loc='chennai';
Output:
1 row deleted.
3. Modifying (Updating) Records:
a. Updating single column
Syntax:
UPDATE <table name> Set <Field Name> = <Value> Where <Condition>;
Example:
SQL> update department set loc='Hyderabad' where deptno=20;
Output:
1 row updated.
Note: Without where clause all the rows will get updated.
b. Updating multiple column [while updating more than one column, the column must be separated by comma operator]
Database Systems Lab Manual
Example: SQL> update department set loc='Hyderabad', dname= ‘cse’ where deptno=20;
Output:
1 row updated.
4. Selection of Records [Retrieving (Displaying) Data:]
Syntax:
Select <field1, field2 …fieldn> from <table name> where <condition>;
Example:
a) SQL> select * from department;
Output:
DEPTNO DNAME LOC
---------- -------------- -------------
10 accounts chennai
20 finance Hyderabad
30 IT Bangalore
40 marketing chennai
Example:
b) SQL> select dname, loc from department;
Output:
DNAME LOC
-------------- -------------
accounts chennai
finance Hyderabad
IT Bangalore
marketing Chennai
 Using Alias name for a field
Syntax:
Select <col1> <alias name 1> , <col2> < alias name 2> from < tab1>;
Example:
SQL> select dname, loc as location from department;
Output:
DNAME LOCATION
-------------- -------------
accounts chennai
Database Systems Lab Manual
finance Hyderabad
IT Bangalore
marketing Chennai
 With distinct clause [Used to retrieve unique value from the column]
Syntax:
Select distinct <col2> from < tab1>;
Example:
SQL> select distinct loc from department;
Output:
LOC
-------------
chennai
Bangalore
Hyderabad
 Creating Table using subquery
Syntax:
Create table <new _table_name> as Select <column names> from <old_table_name>;
Example:
SQL> create table copyOfEmp as select * from employee;
Output:
Table created.
 To view the contents of new Table
SQL> select * from copyofemp;
Output:
EMPLOYEE_ID FIRST_NAME LAST_NAME MANAGER HIRE_DATE JOB_ID SALARY COMMISION DEPTNO
111 Smith Ford 222 21-JUL-10 J1 30000 0.1 1 0
 To create a table with same structure as an existing table
Syntax:
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Create table <new _table_name> as Select <column names> from<old_table_name>
where 1=2;
Example:
create table copyOfEmp2 as select * from employee where 1=2;
Output: Table created.
SQL> select * from copyofemp2;
Output:
no rows selected
SQL> desc copyofemp2;
Output:
Name Null? Type
----------------------------------------- -------- -----------------
EMPLOYEE_ID NUMBER(3)
FIRST_NAME VARCHAR2(10)
LAST_NAME VARCHAR2(10)
MANAGER NUMBER(4)
HIRE_DATE DATE
JOB_ID VARCHAR2(10)
SALARY NUMBER(10)
COMMISION NUMBER(8)
DEPTNO NUMBER(2)
Note: Only structure of table alone is copied and not the contents.
 Inserting into table using a subquery
Syntax :
Insert into <new_table_name> (Select <columnnames> from <old_table_name>);
Example:
SQL> insert into copyofemp2 (select * from employee where employee_id > 100);
Output:
50 rows created.
Database Systems Lab Manual
Constraints
 Constraints enforce rules on the table whenever rows are inserted, updated and deleted from the table.
 Prevents the deletion of a table if there are dependencies from other tables.
 Name a constraints or the oracle server generate name by using SYS_cn format.
 Define the constraints at column or table level. constraints can be applied while creation of table or after the table creation by using alter command.
 View the created constraints from User_Constraints data dictionary.
Constraints Types
CONSTRAINT
DESCRIPTION
NOT NULL
Specifies that a column must have some value.
UNIQUE
Specifies that columns must have unique values.
PRIMARY KEY
Specifies a column or a set of columns that uniquely identifies as row. It does not allow null values.
FOREIGN KEY
Foreign key is a column(s) that references a column(s) of a table.
CHECK
Specifies a condition that must be satisfied by all the rows in a table.
Database Systems Lab Manual
1. Creating Constraints without constraint name
Syntax:
CREATE TABLE < tablename> (
<column name 1> < datatype>,
<column name 2> < datatype> UNIQUE ,
<column name 3> < datatype> ,
PRIMARY KEY ( <column name2>)
);
Example:
CREATE TABLE emp_demo2
( employee_id NUMBER(6) PRIMARY KEY,
first_name VARCHAR2(20) NOT NULL,
last_name VARCHAR2(25) NOT NULL,
email VARCHAR2(25) UNIQUE,
phone_number VARCHAR2(20) UNIQUE,
job_id VARCHAR2(10),
salary NUMBER(8,2) CHECK(SALARY>0),
deptid NUMBER(4)
) ;
2. Creating constraints with constraint name
Syntax:
CREATE TABLE < tablename1> (
<column name 1> < datatype> CONSTRAINT <constraint name1> UNIQUE,
<column name 2> < datatype> CONSTRAINT <constraint name2> NOT NULL,
constraint < constraint name3 > PRIMARY KEY ( <column name1>),
Database Systems Lab Manual
constraint <constraint name4> FOREIGN KEY (<column name2>) REFERENCES <tablename2> (<column name1>)
);
Example:
CREATE TABLE emp_demo3
( employee_id NUMBER(6) CONSTRAINT emp_eid PRIMARY KEY,
first_name VARCHAR2(20),
last_name VARCHAR2(25) CONSTRAINT emp_last_name_nn NOT NULL,
email VARCHAR2(25) CONSTRAINT emp_email_nn NOT NULL,
phone_number VARCHAR2(20),
job_id VARCHAR2(10) CONSTRAINT emp_job_nn NOT NULL,
salary NUMBER(8,2) CONSTRAINT emp_salary_nn NOT NULL,
deptid NUMBER(4), CONSTRAINT emp_dept FOREIGN KEY(deptid)
REFERENCES department(deptid) ,
CONSTRAINT emp_salary_min CHECK (salary > 0) ,
CONSTRAINT emp_email_uk UNIQUE (email)
) ;
3. With check constraint
Syntax:
CREATE TABLE < tablename> (
<column name1 > < datatype> ,
<column name 2> < datatype>,
CHECK ( < column name 1 > in ( values) )
CHECK ( < column name 2 > between <val1> and <val2> ) );
Example:
CREATE TABLE emp_demo4
Database Systems Lab Manual
( emp_id NUMBER(6),
emp_name VARCHAR2(15),
salary NUMBER(10) CHECK (salary between 1000 and 10000)
);
Adding Constriants
Constraints can be added after the table creation by using alter command
Syntax: Add constraints
ALTER TABLE <tablename> ADD CONSTRAINT <constraint_name> constriant_type (<column name>);
Examples:
ALTER TABLE emp_demo4 ADD CONSTRAINT con_pk1 PRIMARY KEY(emp_id);
ALTER TABLE emp_demo4 ADD CONSTRAINT con_emp_uk UNIQUE(phoneno);
ALTER TABLE emp_demo4 ADD CONSTRAINT con_empfk FOREIGN KEY(DNO) REFERENCES department(dno);
ALTER TABLE emp_demo4 ADD CONSTRAINT con_emp_ck CHECK ( salary >0 );
ALTER TABLE emp_demo4 MODIFY (<Column name> <datatype> CONSTRAINT constraint_name NOT NULL);
Drop Constraints
Syntax
ALTER TABLE <tablename> DROP CONSTRAINT < constraint name >;
Drop the unique key on the email column of the employees table:
e.g ALTER TABLE employees DROP UNIQUE (email);
CASCADE Constraints
The CASCADE Constraints clause is used along with the Drop Column Clause.
Database Systems Lab Manual
• A foreign key with a cascade delete means that if a record in the parent table is deleted,
then the corresponding records in the child table will automatically be deleted. This is
called a cascade delete.
• A foreign key with a cascade delete can be defined in either a CREATE TABLE statement or an ALTER TABLE statement.
Syntax:
CREATE TABLE table_name
(column1 datatype null/not null,
column2 datatype null/not null,
...
CONSTRAINT fk_column
FOREIGN KEY (column1, column2, ... column_n)
REFERENCES parent_table (column1, column2, ... column_n)
ON DELETE CASCADE
);
Example:
CREATE TABLE supplier
(supplier_id number(10)not null,
supplier_namevarchar2(50)not null,
contact_namevarchar2(50),
CONSTRAINT supplier_pk PRIMARY KEY (supplier_id));
CREATE TABLE products
(product_id number(10)not null,
suppl_id number(10) not null,
CONSTRAINT fk_supplier FOREIGN KEY (suppl_id) REFERENCES
supplier(supplier_id) ON DELETE CASCADE);
Database Systems Lab Manual
Because of the cascade delete, when a record with a particular supplier_ id is deleted from supplier table , then all the records of the same supplier_id will be deleted from products table also.
Operators in SQL*PLUS
Type
Symbol / Keyword
Where to use
Arithmetic
+ , - , * , /
To manipulate numerical column values, WHERE clause
Comparison
=, !=, <, <=, >, >=, between, not between, in, not in, like, not like
WHERE clause
Logical
and, or, not
WHERE clause, Combining two queries
 Between..And..
Example:
SQL> select first_name, deptno from employee where salary between 20000 and 35000;
Output:
FIRST_NAME DEPTNO
---------- ----------
Smith 10
 IN
Example:
SQL> select first_name, deptno from employee where job_id in ('J1','J2');
Output:
FIRST_NAME DEPTNO
---------- ----------
Smith 10
Database Systems Lab Manual
Arun 30
Nithya 10
 NOT IN
Example:
SQL> select dname,loc from department where loc not in ('chennai','Bangalore');
Output:
DNAME LOC
-------------- -------------
finance Hyderabad
 Like
Use the LIKE condition to perform wild card searches of valid search string values.
Search conditions can contain either characters or numbers
% - denotes zero or many characters.
_ - denotes one character.
Example:
SQL> select dname,loc from department where loc like 'c%';
Output:
DNAME LOC
-------------- -------------
accounts chennai
marketing Chennai
Example:
SQL> select dname,loc from department where loc like 'chen_ _ _';
Output:
DNAME LOC
-------------- -------------
accounts chennai
marketing Chennai
Example:
SQL> select dname,loc from department where loc not like 'c%';
Database Systems Lab Manual
Output:
DNAME LOC
-------------- -------------
finance Hyderabad
IT Bangalore
 Between..and..
Example:
SQL> select first_name, deptno, salary from employee where salary not between 20000 and 35000;
Output:
FIRST_NAME DEPTNO SALARY
---------- ---------- ----------
Arun 30 40000
Nithya 10 45000
Note: Inserting null value into location column of department table
Example:
SQL> insert into department(deptno,dname) values(40,'Sales');
Output:
1 row created.
 is Null
Example:
SQL> select * from department where loc is null;
Output:
DEPTNO DNAME LOC
---------- -------------- -------------
40 Sales
Example:
SQL> select * from department where loc is not null;
Output:
DEPTNO DNAME LOC
Database Systems Lab Manual
---------- -------------- -------------
10 accounts chennai
20 finance Hyderabad
30 IT Bangalore
40 marketing chennai
LOGICAL OPERATORS: Used to combine the results of two or more conditions to produce a single result. The logical operators are: OR, AND, NOT.
Operator Precedence
 Arithmetic operators-Highest precedence
 Comparison operators
 NOT operator
 AND operator
 OR operator----Lowest precedence
The order of precedence can be altered using parenthesis.
Example:
SQL> select first_name, deptno, salary from employee where salary > 20000 ;
Output:
FIRST_NAME DEPTNO SALARY
---------- ---------- ----------
Smith 10 30000
Arun 30 40000
Nithya 10 45000
Example:
SQL> select first_name, deptno, salary from employee
where salary > 20000 and salary < 35000;
Output:
Database Systems Lab Manual
FIRST_NAME DEPTNO SALARY
---------- ---------- ----------
Smith 10 30000
Example:
SQL> select first_name, deptno, salary+100 from employee where salary > 35000;
Output:
FIRST_NAME DEPTNO SALARY+100
---------- ---------- ----------
Arun 30 40100
Example:
SQL> update employee set salary = salary+salary*0.1 where employee_id = 111;
Output:
1 row updated.
Example:
SQL> select * from department where loc = 'chennai' or dname='IT';
Output:
DEPTNO DNAME LOC
---------- -------------- -------------
10 accounts chennai
30 IT Bangalore
40 marketing chennai
FUNCTIONS
 Single Row Functions
 Group functions
Single Row Functions
Returns only one value for every row can be used in SELECT command and included in WHERE clause
Types
 Character functions
Database Systems Lab Manual
 Numeric functions
 Date functions
CHARACTER FUNCTIONS:
Character functions accept a character input and return either character or number values. Some of them supported by Oracle are listed below
Syntax
Description
initcap (char)
Changes first letter to capital
lower (char)
Changes to lower case
upper (char)
Changes to upper case
ltrim ( char, set)
Removes the set from left of char
rtrim (char, set)
Removes the set from right of char
translate(char, from, to)
Translate ‘from’ anywhere in char to ‘to’
replace(char, search string, replace string)
Replaces the search string to new
substr(char, m , n)
Returns chars from m to n length
lpad(char, length, special char)
Pads special char to left of char to Max of length
rpad(char, length, special char)
Pads special char to right of char to Max of length
chr(number)
Returns char equivalent
length(char)
Length of string
Examples:
Function
Input
Output
Initcap(char)
SQL>select initcap(‘hello’) from dual;
Hello
Lower(char)
SQL>select lower(‘FUN’) from dual;
fun
Database Systems Lab Manual
Upper(char)
SQL>select upper(‘sun’) from dual;
SUN
Ltrim(char, set)
SQL>select ltrim(‘xyzhello’,’xyz’) from dual;
hello
Rtrim(char, set)
SQL>select rtrim(‘xyzhello’,’llo’) from dual;
xyzhe
translate(char,from,to)
SQL>select translate(‘jack’,’j’,’b’) from dual;
back
Replace(char,from,to)
SQL>select replace(‘jack and jue’,’ j’, ’bl’) from dual;
black and blue
Example:
SQL> select initcap(dname) from department;
Output:
INITCAP(DNAME)
--------------
Accounts
Finance
It
Marketing
Sales
Lpad is a function that takes three arguments. The first argument is the character string which has to be displayed with the left padding. The second is the number which indicates the total length of the return value, the third is the string with which the left padding has to be done when required.
Example:
SQL> select lpad(dname,15,'*') lpd from department;
Output:
LPD
---------------
*******accounts
********finance
*************IT
******marketing
**********Sales
Example:
SQL> select rpad(dname,15,'*') rpd from department;
Output:
Database Systems Lab Manual
RPD
---------------
accounts*******
finance********
IT*************
marketing******
Sales**********
Length: returns the length of a string
Example:
SQL> select dname, length(dname) from department;
Output:
DNAME LENGTH(DNAME)
-------------- -------------
accounts 8
finance 7
IT 2
marketing 9
Sales 5
Concatenation operator ||: is used to merge or more strings.
Example:
SQL> select dname || ' is located in ' || loc from department;
Output:
DNAME||'ISLOCATEDIN'||LOC
------------------------------------------
accounts is located in chennai
finance is located in Hyderabad
IT is located in Bangalore
marketing is located in chennai
Sales is located in
NUMERIC FUNCTIONS:
Numeric functions accept numeric input and returns numeric values as output.
Database Systems Lab Manual
Syntax
Description
abs ( )
Returns the absolute value
ceil ( )
Rounds the argument
cos ( )
Cosine value of argument
exp ( )
Exponent value
floor( )
Truncated value
power (m,n)
N raised to m
mod (m,n)
Remainder of m / n
round (m,n)
Rounds m’s decimal places to n
trunc (m,n)
Truncates m’s decimal places to n
sqrt (m)
Square root value
Examples:
Function
Input
Output
Abs( n)
SQL>select abs(-15) from dual
15
Ceil(n)
SQL>select ceil(48.778) from dual;
49
Cos(n)
SQL>select cos(180) from dual;
-0.59884601
Cosh(n):
SQL>select cosh(0) from dual;
1
Exp(n)
SQL>select exp(4) from dual;
54.59815
Floor(n)
SQL>select floor(4.678) from dual;
4
Power(m ,n)
SQL>select power(5,2) from dual;
25
Mod(m ,n)
SQL>select mod(11,2) from dual;
1
Round(m ,n)
SQL>select round(112.257,2) from dual;
112.26
Example:
SQL> select ln (2) from dual; (returns natural logarithm value of 2)
Database Systems Lab Manual
SQL>select sign (-35) from dual; (output is -1)
CONVERSION FUNCTIONS: Convert a value from one data type to another.
 To_char ( )
To_ char (d [,fmt]) where d is the date fmt is the format model which specifies the format of the date. This function converts date to a value of varchar2datatype in a form specified by date format fmt.if fmt is neglected then it converts date to varchar2 in the default date format.
Example:
SQL> select to_char (hire_date, 'ddth "of" fmmonth yyyy') from employee;
Output:
TO_CHAR(HIRE_DATE,'DDT
----------------------
21st of july 2010
05th of june 2008
12th of february 1999
 To_ date ( )
The format is to_date (char [, fmt]). This converts char or varchar data type to date data type. Format model, fmt specifies the form of character.
Example:
SQL>select to_date (‘December 18 2007’,’month-dd-yyyy’) from dual;
Output:
18-DEC-07 is the output.
Example:
SQL> select round(hire_date,'year') from employee;
Output:
ROUND(HIR
---------
01-JAN-11
01-JAN-08
01-JAN-99
 To_ Number( )
Database Systems Lab Manual
Allows the conversion of string containing numbers into the number data type on which arithmetic operations can be performed.
Example: SQL> select to_number (‘100’) from dual;
DATE FUNCTIONS
Example:
SQL> select sysdate from dual;
Output:
SYSDATE
---------
22-JUL-10
Example:
SQL> select hire_date from employee;
Output:HIRE_DATE
---------
21-JUL-10
05-JUN-08
Function Name
Return Value
ADD_MONTHS (date, n)
Returns a date value after adding ’n’months to the date ’x’.
MONTHS_BETWEEN (x1, x2)
Returns the number of months between dates x1 and x2.
ROUND (x, date_format)
Returns the date ‘x’rounded off to the nearest century, year, month, date, hour, minute, or second as specified by the ‘date_format’.
TRUNC (x, date_format)
Returns the date ‘x’ lesser than or equal to the nearest century, year, month, date, hour, minute, or second as specified by the ‘date_format’.
NEXT_DAY (x, week_day)
Returns the next date of the ‘week_day’on or after the date ‘x’ occurs.
LAST_DAY (x)
It is used to determine the number of days remaining in a month from the date 'x'specified.
SYSDATE
Returns the systems current date and time.
Database Systems Lab Manual
12-FEB-99
Example:
SQL> select add_months(hire_date,3) from employee;
Output:
ADD_MONTH
---------
21-OCT-10
05-SEP-08
12-MAY-99
Example:
SQL> select months_between(sysdate,hire_date) from employee;
Output:
MONTHS_BETWEEN(SYSDATE,HIRE_DATE)
---------------------------------
.047992085
25.5641211
137.338315
Example:
SQL> select next_day(hire_date,'wednesday') from employee;
Output:
NEXT_DAY(
---------
28-JUL-10
11-JUN-08
17-FEB-99
Example:
SQL> select last_day(hire_date) from employee;
Output:
LAST_DAY(
---------
31-JUL-10
30-JUN-08
28-FEB-99
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Group Functions: - Group functions are built-in SQL functions that operate on groups of rows and return one value for the entire group. These functions are: COUNT, MAX, MIN, AVG, SUM, DISTINCT
 Group functions operate on sets of rows to give one result per group of Employees
Dept_id
Salary
90
5000
90
10000
90
10000
60
5000
60
5000
Types of Group Functions
Syntax
Description
count (*),
count (column name),
count (distinct column name)
Returns number of rows
min (column name)
Min value in the column
max (column name)
Max value in the column
avg (column name)
Avg value in the column
sum (column name)
Sum of column values
The maximum salary in the employees table
Max (salary) 10000
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Group Functions Syntax:
Select [column,] group_function(column),..
From table
[where condition]
[GROUP BY column];
Example:
Q.Display the average,highest, lowest and sum of salaries for all the sales representatives.
A. Select avg(salary), max(salary), min(salary), sum(salary) From employees where job_id like ‘%rep%’;
Groups of Data : Divide rows in a table in to smaller groups by using the group by clause
Employee Table
Dept_id
Salary
10
4000
10
5000
10
6000
50
5000
50
3000
SET OPERATORS: UNION,UNION ALL,DIFFERENCE,MINUS
Example:
sql> select first_name from employees union select name from sample ;
Output:
FIRST_NAME
----------
DHANA
GUNA
D_id
Avg(Salary)
10
5000
50
4000
The average salary in employees table for each department
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JAI
JAISANKAR
KUMAR
RAJA
VENKAT
Example:
sql> select first_name from employees union all select name from sample ;
Output:
FIRST_NAME
----------
VENKAT
JAI
DHANA
GUNA
JAISANKAR
VENKAT
RAJA
KUMAR
Example:
sql> select first_name from employees intersect select name from sample ;
Output:
FIRST_NAME
----------
VENKAT
Example:
sql> select first_name from employees minus select name from sample ;
Output:
FIRST_NAME
----------
DHANA
GUNA
JAI
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 JOINS :A join is the SQL way of combining the data from many tables. It is performed by WHERE Clause which combines the specified rows of the tables.
Type
Sub type
Description
Simple join
Equi join ( = )
Non – equi join (<, <=, >, >=, !=, < > )
Joins rows using equal value of the column
Joins rows using other relational operators(except = )
Self join
-- ( any relational operators)
Joins rows of same table
Outer join
Left outer join ((+) appended to left operand in join condition)
Right outer join ((+) appended to right operand in join condition)
Rows common in both tables and uncommon rows have null value in left column
Vice versa
Simple Join:
a. EQUI JOIN OR INNER JOIN : A column (or multiple columns) in two or more tables match.
Syntax:
SELECT <column_name(s)> FROM <table_name1> INNER JOIN <table_name2> ON <table_name1.column_name>=<table_name2.column_name>;
Example 1 :
SELECT employee.first_name, department.dname FROM employee INNER JOIN department
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ON employee.deptno = department.deptno; Output:1
DEPTNO FIRST_NAME
---------- ----------
10 Smith
30 Arun
10 Nithya
Oracle automatically defaults the JOIN to INNER so that the INNER keyword is not required. They are the same query, though. It is preferred not to type the INNER keyword. Example 2 using where Condition:
SELECT employee.ename, department.dname FROM employee JOIN department ON employee.deptno = department.deptno WHERE department.dname = 'SALES'; Output 2:
DEPTNO FIRST_NAME
---------- ----------
10 Smith
30 Arun
10 Nithya
b. SELF JOIN: Is a join where a table is joined to itself.
Syntax:
SELECT <column_name(s)> FROM <table_name1> JOIN <table_name2> ON <table_name1.column_name>=<table_name1.column_name>;
Example1:
SELECT e1.first_name, e2.first_name
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FROM employee e1 join employee e2
on e1.mgr = e2.employee_id;
OR
SELECT e1.first_name, e2.first_name
FROM employee e1 join employee e2
where e1.mgr = e2.employee_id;
Output:
FIRST_NAME FIRST_NAME
---------------- --------------------
john john
An alias is just a way to refer to a column or table with a UNIQUE name. If we try to call both of the instances of the table EMP, Oracle wouldn't know which table instance we refer to. Using an alias clears this confusion
c. OUTER JOIN
An outer join tells Oracle to return the rows on the left or right (of the JOIN clause) even if there are no rows. The LEFT OUTER keyword to the JOIN clause says, return the rows to the left (in this case DEPARTMENT) even if there are no rows on the right (in this case employee). Syntax:
SELECT <column_name(s)> FROM <table_name1> LEFT OUTER JOIN <table_name2> ON <table_name1.column_name>=<table_name2.column_name>;
Example:
SELECT department.dname, employee.first_name
FROM department LEFT OUTER JOIN employee ON department.deptno = employee.deptno WHERE department.dname = 'marketing’;
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Output:
DNAME FIRST_NAME
-------------- ----------
Marketing
The RIGHT OUTER keyword to the JOIN clause says ,return the rows to the right relation (in this case DEPARTMENT) even if there are no matching rows on the left relation (in this case employee). Syntax:
SELECT <column_name(s)> FROM <table_name1> RIGHT OUTER JOIN <table_name2> ON <table_name1.column_name>=<table_name2.column_name>;
Example:
SELECT employee.first_name, department.dname FROM employee RIGHT OUTER JOIN department ON employee.deptno = department.deptno WHERE department.dname = 'marketing';
Output:
FIRST_NAME DNAME
---------- --------------
marketing
d. FULL OUTER JOIN
Let's insert a new record into the employee table:
INSERT INTO EMPLOYEE (employee_id, first_name, last_name, mgr, hiredate, job-id,sal, comm, deptno) VALUES (9999, 'Joe ‘,’Blow', 7698, sysdate ,0008, 10500, 0, NULL ); Note:
We inserted an employee record that has no department. How can we get the records for
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all employees AND all departments? We would use the FULL OUTER join syntax: Syntax:
SELECT <column_name(s)> FROM <table_name1> FULL OUTER JOIN <table_name2> ON <table_name1.column_name>=<table_name2.column_name>;
Example:
SELECT employee.first_name, department.dname FROM employee FULL OUTER JOIN department ON employee.deptno = department.deptno; Output:
FIRST_NAME DNAME
---------- --------------
Nithya accounts
Smith accounts
finance
john IT
Arun IT
marketing
john
e.Cross Join
Displays all the rows and all the colums of both the tables.
Synatx:
SELECT <column_name(s)> FROM <table_name1> CROSS JOIN<table_name2>;
Example:
select employee.deptno from employee cross join department;
Or
select employee.deptno from employee,department;
Output:
DEPTNO
----------
10
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10
10
10
30
30
30
30
10
10
10
DEPTNO
----------
10
30
30
30
30
f. Natural Join
If two tables have same column name the values of that column will be displayed only once.
Syntax:
SELECT <column_name(s)> FROM <table_name1> Natural JOIN<table_name2>;
Example:
select deptno,first_name from employee natural join department;
Output:
DEPTNO FIRST_NAME
------ ----------
10 Smith
30 Arun
10 Nithya
30 john
SUB QUERIES
 Nesting of queries
 A query containing a query in itself A
 Inner most sub query will be executed first
 The result of the main query depends on the values return by sub query
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 Sub query should be enclosed in parenthesis
1. Sub query returning only one value
a. Relational operator before sub query.
Syntax:
SELECT <column_name(s)> FROM <table_name> WHERE < column name >
< relational op.> < sub query>;
Example:
SELECT employee_id ,first_name FROM employee
WHERE deptno =
(SELECT deptno FROM department
WHERE dname = ‘IT’)
Output:
EMPLOYEE_ID FIRST_NAME
----------- ----------
112 Arun
114 john
2. Sub query returning more than one value
a. ANY
For the clause any, the condition evaluates to true if there exists at least one row selected by the sub query for which the comparison holds. If the sub query yields an empty result set, the condition is not satisfied.
Syntax:
SELECT <column_name(s)> FROM <table_name> WHERE < column name >
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< relational op.> ANY (<sub query>);
Example:
SELECT employee_id ,first_name FROM employee
WHERE salary>= ANY
(SELECT salary FROM employee
WHERE deptno = 30)
AND deptno = 10;
Output:
EMPLOYEE_ID FIRST_NAME
----------- ----------
113 Nithya
112 Arun
111 Smith
114 john
114 john
b. ALL
For the clause all, in contrast, the condition evaluates to true if for all rows selected by the sub query the comparison holds. In this case the condition evaluates to true if the Sub query does not yield any row or value.
Syntax:
SELECT <column_name(s)> FROM <table_name> WHERE < column name > < relational op.> ALL (<sub query>);
Example:
SELECT employee_id ,first_name FROM employee
WHERE salary > ALL
(SELECT salary FROM employee
WHERE deptno = 30);
Output:
EMPLOYEE_ID FIRST_NAME
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----------- ----------
113 Nithya
c. IN :Main query displays the values that match with any of the values returned by sub query.
Syntax:
SELECT <column_name(s)> FROM <table_name>
WHERE < column name > IN (<sub query>);
Example:
SELECT employee_id ,first_name FROM employee
WHERE deptno IN
(SELECT deptno FROM department
WHERE loc = ’Bangalore’);
Output:
EMPLOYEE_ID FIRST_NAME
----------- ----------
114 john
112 Arun
d. NOT IN
Main query displays the values that match with any of the values returned by sub query.
Syntax:
SELECT <column_name(s)> FROM <table_name> WHERE < column name > NOT IN (<sub query>);
Example:
SELECT employee_id ,first_name FROM employee
WHERE deptno NOT IN
(SELECT deptno FROM department
WHERE loc = ’Bangalore’);
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Output:
EMPLOYEE_ID FIRST_NAME
----------- ----------
113 Nithya
111 Smith
e. EXISTS
Main query displays the values that match with any of the values returned by sub query.
Syntax:
SELECT <column_name(s)> FROM <table_name> WHERE EXISTS (<sub query>);
Example:
SELECT * FROM department
WHERE EXISTS
(SELECT * FROM employee
WHERE deptno = department.deptno);
Output:
DEPTNO DNAME LOC
---------- -------------- -------------
10 accounts chennai
30 IT Bangalore
f. NOT EXISTS
Main query displays the values that match with any of the values returned by sub query.
Syntax:
SELECT <column_name(s)> FROM <table_name> WHERE NOT EXISTS (<sub query>);
Example:
SELECT * FROM department
WHERE NOT EXISTS
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(SELECT * FROM employee
WHERE deptno = department.deptno);
Output:
DEPTNO DNAME LOC
---------- -------------- -------------
20 finance Hyderabad
40 marketing chennai
g. GROUP BY CLAUSE
Often applications require grouping rows that have certain properties and then applying an aggregate function on one column for each group separately. For this, SQL provides the clause group by <group column(s)>. This clause appears after the where clause and must refer to columns of tables listed in the from clause.
Rule:
Select attributes and group by clause attributes should be same.
Syntax:
SELECT <column_name(s)> FROM <table_name> Where <conditions>
GROUP BY <column2>, <column1>;
Example:
SELECT deptno, min(salary), max(salary)
FROM employee
GROUP BY deptno;
Output:
DEPTNO MIN(SALARY) MAX(SALARY)
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--------- ----------- -----------
30 30000 40000
30000 30000
10 33000 45000
h. HAVING CLAUSE: used to apply a condition to group by clause
Syntax:
SELECT <column(s)>
FROM <table(s)>
WHERE <condition>
[GROUP BY <group column(s)>]
[HAVING <group condition(s)>];
Example:
SELECT deptno, min(salary), max(salary)
FROM employee
WHERE job_id = ’J2’
GROUP BY deptno
HAVING count(*) > 1;
Output:
DEPTNO MIN(SALARY) MAX(SALARY)
---------- ----------- -----------
30 13000 40000
A query containing a group by clause is processed in the following way:
1. Select all rows that satisfy the condition specified in the where clause.
2. From these rows form groups according to the group by clause.
3. Discard all groups that do not satisfy the condition in the having clause.
4. Apply aggregate functions to each group.
5. Retrieve values for the columns and aggregations listed in the select clause.
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i. ORDER BY
Used along with where clause to display the specified column in ascending order or descending order . Default is ascending order
Syntax:
SELECT [distinct] <column(s)>
FROM <table>
[ WHERE <condition> ]
[ ORDER BY <column(s) [asc|desc]> ]
Example:
SELECT first_name, deptno, hire_date
FROM employee
ORDER BY deptno ASC, hire_date desc;
Output:
FIRST_NAME DEPTNO HIRE_DATE
---------- ---------- ---------
Smith 10 21-JUL-10
Nithya 10 12-FEB-99
john 30 20-JAN-10
Arun 30 05-JUN-08
john 20-JAN-10
VIEWS
Definition: A view is a named, derived, virtual table. A view takes the output of a query and treats it as a table; therefore a view can be thought of as a ‘stored query’ or a ‘virtual table’. We can use views in most places where tables can be used. To the user, accessing a view is like accessing a table. The RDBMS creates an illusion of a table, by assigning a name to the view and storing its definition in the database.
The tables upon which the views are based are called as ‘base tables’.
CREATION OF A VIEW:
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The syntax for creating a view is given by:
create [or replace][[no][force]]view <view_name> [column alias name…]as <query>[with[check option]read only][constraint]];
Example:
SQL>create or replace view EMP_VIEW as select * from EMP;
This statement creates a view named EMP_VIEW .The data in this view comes from the base table EMP. Any changes made to the base table are instantly visible through the view EMP_VIEW.We can use select statement just like on a table.
SQL>select * from EMP_VIEW;
When create or replace is given, view is created if it is not available otherwise it is recreated.
HOW DOES RDBMS HANDLE THE VIEWS: When a reference is made by a user, the RDBMS finds the definition of the view stored in the database .It then translates the user’s request that referenced the view into an equivalent request against the source tables of the view. Thus RDBMS maintains the illusion of the view.
TYPES OF VIEWS: The different types of views are
• Column subset view
• Row subset view
• Row-Column subset view
• Grouped view
• Joined view
COLUMN SUBSET VIEW:
A column subset view is one where all the rows but only some of the columns of the base table form the view. The create view
Example:
SQL>create or replace view CSV as select empno, ename, sal from EMP;
This view includes only columns empno, ename, sal of EMP table. Since there is no where clause it includes all the rows.
ROW SUBSET VIEW:
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A row subset view is one where all columns but some rows of the source table form the view. All the columns of the base table participate in the view but all rows do not.
Example:
SQL> create or replace view RSV as select * from EMP where deptno=10;
The where clause restricts the no. of rows to those of employees working in Department Number 10.
ROW-COLUMN SUBSET VIEW:
A row-column subset view is a view which includes only some rows and columns of the base table.
Example:
SQL>create or replace view RCS as select EMPNO, ENAME, SAL from EMP where deptno=10;
GROUPED VIEW:
The query specified in the view definition can include the GROUP BY clause. This type of view is called as Grouped View.
Example:
SQL>create or replace view GV (dno, avgsal) as select deptno, AVG (SAL) from emp group by deptno;
JOINED VIEWS:
A joined view is formed by specifying a two or more table query in the view definition. A joined view draws its data from two or more tables and presents the result as a single virtual table.
Example:
SQL>create or replace view JV(empno,ename,sal,dname,loc) as select empno,ename,sal,dname,loc from EMP,DEPT where EMP.deptno=DEPT.deptno;
CREATING A READ ONLY VIEW:
Use with read only clause to prevent the users from manipulating records via the view.
Example:
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SQL>create or replace view WRO as select * from EMP with read only;
Note: A view can be created without a base table using FORCE option of create view command.
Example:
SQL>create or replace force view FVIEW as select * from MYDEPT;
In this query MYDEPT table does not exist, so view is created with compilation errors. When MYDEPT table is created and this query is executed, the view is automatically recompiled and become valid.
VIEW WITH CHECK OPTION:
This option specifies that inserts and updates performed through the view must result in rows that the view query can select. The CHECK OPTION can be used to maintain integrity on a view.
Example:
SQL>insert into RSV (empno, ename, sal, deptno) values (1000,’dinesh’, 5500, 20);
Though the view is created for deptno 10, we are able to insert records for other department numbers .This can be restricted using WITH CHECK OPTION clause while creating a view.
Example:
SQL>create view DEPTNO10_VIEW as select * from EMP where deptno=10 WITH CHECK OPTION CONSTRAINT CHK_DNO10;
The above statement creates a view DEPTNO10 with a check constraint. This will enforce the view to be inserted or updated only for the department number 10. No other departments can be inserted or updated.
DROPPING A VIEW:
A view can be dropped by using DROP VIEW command.A view becomes invalid if its associated base table is dropped.
Example:
SQL>drop view DEPTNO10;
This will not affect the base table EMP.
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ADVANTAGES OF VIEWS:
 Valid Information: Views let different users see a table from different perspectives. Only the part that is relevant to the users is visible to them.
 Restricted Access: Views restrict access to the table. Different users are allowed to see only certain rows or certain columns of a table.
 Simplified Access: Views simplify database access. For example a view that is a join of three tables where a user does not require all the data in all three tables.
 Data Integrity: Data Integrity can be maintained by having WITH CHECK OPTION while creating a view.
RESTRICTIONS ON VIEWS:
 A view’s query cannot select the CURRVAL or NEXTVAL pseudo columns.
 If a view’s query selects the ROWID, ROWNUM or LEVEL pseudo columns, they must have aliases in the view’s query.
 A view can’t be created with an ORDER BY clause.
 A view can’t be updated, deleted and inserted if it is a grouped view.
 A view created from multiple tables can’t be updatable.
 If a view is based on a single underlying table then you can insert, update or delete rows in this view. This will actually insert, update or delete rows in the underlying table. There are restrictions again on doing this:
 You cannot insert if the underlying table has a NOT NULL column that does not appear in the view.
 You cannot insert or update if any of the view’s columns referenced in insert or update consist of functions or calculations.
 You cannot insert, update or delete if the view contains GROUP BY, DISTINCT or a reference to a pseudo column ROWNUM.
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PL/SQL
Overview of PL/SQL
PL/SQL is the procedural extension to SQL with design features of programming languages. Data manipulation and query statements of SQL are included within procedural units of code.
Pl/SQL Environment
The PL/SQL engine in the oracle server process the pl/sql block and it separates SQL staments and sends them individually to the SQL statements executor
Benefits of PL/SQL
 Integration
 Improved performance
 Modularized program development
 Portability
 Identifiers
PL/SQL engine
P SQL
SQL
PL/SQL block
Procedural statement executor
PL/SQL block
Oracle Server
SQL statement executor
Database Systems Lab Manual
PL/SQL Block structure
DECLARE (optional)
Variables, cursors, user-defined exceptions
BEGIN (Mandatory)
-SQL statements
-PL/SQL statements
EXCEPTION (optional)
Action to perform when error occur
END;
The PL/SQL Block consists of three sections:
DECLARATIVE
It contains all variables, constants, cursors and user defined exceptions that are referenced in the executable and declarative sections.
EXECUTABLE
It contains SQL statements to manipulate data in the database and PL/SQL statements to manipulate data in the block.
EXCEPTION HANDLING
It specifies the actions to perform when errors and abnormal conditions arise in the executable section.
PL/SQL Block Types
A PL/SQL program comprises one or more blocks.
It is classified into two blocks
 Anonymous Blocks
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It is unnamed blocks. It is declared at the point in an application where they are to be executed and are passed to the PL/SQL engine for execution at run time.
 Subprograms
Subprograms are named PL/SQL blocks that can accept parameters and can be invoked. It can be declared either as procedures or as functions.
Sample PL/SQL programs
To write PL/SQL programs, create a script file and run the script file or use editor.
Steps to create script file
Step1:
SQL> edit z:\oracle\sql\var1.sql
Step2:
Type the program in notepad
Step 3:
Save the program
Step4:
Run the program
SQL> @z:\oracle\sql\var1.sql
SQL> set serveroutput on;
This command is used to display the statement executed by dbms_output.put_line package.
Program 1: Write a program to print a variable value.
SQL> declare
2 a number:=3;
3 begin
Database Systems Lab Manual
4 dbms_output.put_line(a);
5 end;
6 /
3
Program 2: Write a program to print your name and regno.
1 declare
2 v_name varchar2(10);
3 v_regno number;
4 begin
5 v_name:='venkat';
6 v_regno:=39;
7 dbms_output.put_line( 'the name is' || v_name);
8 dbms_output.put_line('the no is' || v_regno);
9 end;
SQL> /
the name is venkat
the no is 39
PL/SQL procedure successfully completed.
Database Systems Lab Manual
Program 3: Write a program to retrieve ssn number of employee whose name is x.
Assume the following table:
SSN NAME ESSN DEPTNO SALARY
---------- ---------- ---------- ---------- ----------
101 x 102 1
102 y 103 2
103 z 102 3
104 p 102 4
105 q
declare v_no number;
begin
select ssn into v_no from emp where name='x';
dbms_output.put_line(v_no);
end;
SQL>/
101
PL/SQL procedure successfully completed.
SCALAR VARIABLE
It holds a single value and has no internal components.
Examples : number, character, date, boolean
Example: using scalar variable
Database Systems Lab Manual
1 declare
2 v_name varchar2(10);
3 V_count binary_integer:=10;
4 V_totalsal number(9,2);
5 v_orderdate date:=sysdate;
6 c_tax constant number(3,2):=6.23;
7 v_valid boolean not null:=true;
8 v_regno number default 23;
9 begin
10 v_name:='venkat';
11 v_totalsal:=10000.23;
12 dbms_output.put_line(v_name);
13 dbms_output.put_line(v_count);
14 dbms_output.put_line(v_orderdate);
15 dbms_output.put_line(c_tax);
16 dbms_output.put_line(v_regno);
17 end;
18 /
venkat
10
19-AUG-05
6.23
23
Database Systems Lab Manual
DECLARING VARIABLE WITH THE %TYPE ATTRIBUTE
The % type attribute is used to declare a variable according to:
1. A database column definition
2. Another previously declared variable
Example: using % type attribute
1 declare
2 v_no emp.ssn%type;
3 V_name varchar2(10):='venkat';
4 name v_name%type;
5 begin
6 v_no:=10;
7 name:='ven';
8 dbms_output.put_line(v_no);
9 dbms_output.put_line(name);
10*end;
11 /
10
ven
PL/SQL procedure successfully completed.
Database Systems Lab Manual
BIND VARIABLES
A bind variable is a variable that is declared in a host environment. Bind variables can be used to pass run-time values, which can be either number or character, into or out of one or more PL/SQL programs.
Example:
SQL> variable a number;
SQL> ed
File:
1 begin
2 select ssn into:a from emp where name='x';
3 dbms_output.put_line(:a);
4 end;
SQL> /
101
PL/SQL procedure successfully completed.
SQL> print a;
A
----------
101
PL/SQL procedure successfully completed.
Database Systems Lab Manual
REFERENCING NON PL/SQL VARIABLES
To reference host variables, prefix the references with a colon (:) to distinguish them from declared PL/SQL variable.
SQL> variable gg number;
SQL> define aa=1000;
SQL> set verify off
SQL> declare
2 v_sal number(9,2):=&aa;
3 begin
4 :gg:=v_sal/12;
5 end;
6 /
PL/SQL procedure successfully completed.
SQL> print gg;
GG
----------
83.3333333
PL/SQL BLOCK SYNTAX AND GUIDELINES
A line of pl/sql text contains groups of characters known as lexical units.
Lexicals are classified as follows:
 Delimiters
 Identifiers, which include reserved words
 Literals
 Character literals
 Numeric literals
Database Systems Lab Manual
COMMENTS:
-- single line commenting
/* beginning */ ending
PL/SQL HAS ITS OWN ERROR HANDLING:
 SQLCODE
 SQL ERRM
DATA TYPE CONVERSION
PL/SQL performs implicit conversions. For E.g. numeric to char.
The following program highlights conversion involving DATE.
SQL> ed
1 declare
2 vdate date;
3 begin
4 vdate:=to_date('aug 19 ,2005','mon dd,yyyy');
5 dbms_output.put_line(vdate);
6 end;
SQL> /
19-AUG-05
PL/SQL procedure successfully completed.
Database Systems Lab Manual
SQL FUNCTIONS IN PL/SQL:
All SQL functions are allowed except decode function and group functions.
NESTED BLOCKS AND VARIABLE SCOPE
SQL> declare
2 v_a number:=3;
3 begin
4 declare
5 v_b number:=4;
6 begin
7 dbms_output.put_line(v_b);
dbms_output.put_line(v_a);
8 end;
9 dbms_output.put_line(v_a);
10 end;
11 /
4
3
PL/SQL procedure successfully completed.
Database Systems Lab Manual
QUALIFYING AN IDENTIFIER An identifier is qualified by using the block label prefix. In the example the outer block is labeled as outer. In the inner block the variable is reference by label, when variable names are same.
SQL> ed
1 <<outer>>
2 declare
3 v_a number:=3;
4 begin
5 declare
6 v_a number:=4;
7 begin
8 dbms_output.put_line(v_a);
9 dbms_output.put_line(outer.v_a);
10 end;
11 end;
12 /
4
3
PL/SQL procedure successfully completed.
Database Systems Lab Manual
PROGRAMMING GUIDELINES:
Category
Case Conversion
Examples
SQL statements
uppercase
SELECT,INSERT
PL/SQL statements
uppercase
DECLARE,BEGIN,IF
Data types
uppercase
VARCHAR2,BOOLEAN
Identifiers
lowercase
v_sal
Database tables and column
lowercase
emp, dept
INTERACTING WITH ORACLE SERVER:
 Extracts row of data from the database using select
 Effects changes in the database by using DML commands
 Controls a transaction with commit, rollback and save point
NOTES:
 An end in pl/sql block is not the end of transaction.
 A block can span multiple transactions, a transaction can span multiple blocks.
 DDL commands (create,alter,drop) and DCL commands(grant,revoke) are not directly supported.
SQL> select * from emp;
SSN NAME ESSN DEPTNO SALARY
---------- ---------- ---------- ---------- ----------
101 x 102 1
Database Systems Lab Manual
102 y 103 2
103 z 102 3
104 p 102 4
105 q
SQL> ed
1 declare
2 v_ssn number;
3 v_name varchar2(10);
4 begin
5 select ssn,name into v_ssn,v_name from emp where name='x';
6 dbms_output.put_line(v_ssn);
7 dbms_output.put_line(v_name);
8 end;
SQL> /
101
x
PL/SQL procedure successfully completed.
RETRIEVING DATA IN PL/SQL:
SQL> select * from job_grade;
GRA LOWEST_SAL HIGHEST_SAL
---- ---------- -----------------------------------------
a 3000 4000
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b 5000 6000
c 3000 6000
d 4000 10000
e 2000 6000
SQL> ed
1 declare
2 v_lsal job_grade.lowest_sal%type;
3 v_hsal job_grade.highest_sal%type;
4 begin
5 select sum(lowest_sal),sum(highest_sal) into v_lsal,v_hsal from job_grade;
6 dbms_output.put_line(v_lsal);
7 dbms_output.put_line(v_hsal);
8 end;
9 /
17000
32000
PL/SQL procedure successfully completed.
NAMING CONVENTIONS
A local variable in pl/sql name must not be equal to column names present in database .
declare
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lastname varchar2(10);
begin
delete from emp where lastname-lastname;
The above code will delete all employees because of the naming convention problem.
MANIPULATING DATA USING PL/SQL
SUBSTIUTION VARIABLE:
SQL> ed
Wrote file afiedt.buf
1 declare
2 v_sal number;
3 begin
4 v_sal:=&v_sal;
5 dbms_output.put_line(v_sal);
6 end;
7 /
Enter value for v_sal: 2000
2000
PL/SQL procedure successfully completed.
INSERTION
SQL> ed
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Wrote file afiedt.buf
1 begin
2 insert into emp(ssn,name) values(123,'venkat');
3 dbms_output.put_line('record inserted');
4 end;
5 /
record inserted
PL/SQL procedure successfully completed.
USAGE OF SUBSTITUTION VARIABLE:
SQL> ed
Wrote file afiedt.buf
1 begin
2 insert into emp(ssn,name) values(&ssn,'&name');
3 dbms_output.put_line('record inserted');
4 end;
SQL> /
Enter value for ssn: 124
Enter value for name: sampath
record inserted
PL/SQL procedure successfully completed.
Database Systems Lab Manual
UPDATE:
SQL> ed
Wrote file afiedt.buf
1 declare
2 v_sal number;
3 begin
4 v_sal:=&v_sal;
5 update job_grade set lowest_sal=v_sal where gra='a';
6 dbms_output.put_line('record updated');
7 end;
SQL> /
Enter value for v_sal: 12000
record updated
PL/SQL procedure successfully completed.
SQL> select *from job_grade;
GRA LOWEST_SAL HIGHEST_SAL
---- ---------- -------------------------------------------
a 12000 4000
b 5000 6000
c 3000 6000
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d 4000 10000
e 2000 6000
DELETE:
SQL> ed
Wrote file afiedt.buf
1 declare
2 v_sal number;
3 begin
4 v_sal:=&v_sal;
5 delete from job_grade where lowest_sal=v_sal;
6 dbms_output.put_line('record deleted');
7 end;
8 /
Enter value for v_sal: 5000
record deleted
PL/SQL procedure successfully completed.
SQL> select * from job_grade;
GRA LOWEST_SAL HIGHEST_SAL
---- ---------- -----------
a 12000 4000
c 3000 6000
d 4000 10000
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e 2000 6000
CONTROL STRUCTURES
• IF statements
 If –then-end if
 If-then-else-end if
 If-then-elseif-end if
• Case expressions
• Loop statements
 Basic loops
 While loops
 For loops
Syntax of IF:
If condition then
Statements;
Else if condition then
Statements;
Else
Statements;
End if;
Examples:
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1) Find the greatest among two numbers
1 declare
2 a number;
3 b number;
4 begin
5 a:=&a;
6 b:=&b;
7 if a>b then
8 dbms_output.put_line('gratest number is'||a);
9 else
10 dbms_output.put_line('gratest number is'||b);
11 end if;
12 end;
SQL> /
Enter value for a: 12 old 5: a:=&a;
new 5: a:=12;
Enter value for b: 4 old 6: b:=&b;
new 6: b:=4;
greatest number is12
PL/SQL procedure successfully completed
Database Systems Lab Manual
2) if else with database
DEPT_ID
DEPT_NAME
MANAGER_ID
LOCATION_ID
---------
----------
----------
-----------
10
cse
200
1700
20
it
300
1800
30
mech
400
1500
40
ece
500
1600
1 declare
2 v_id departments.dept_id%type;
3 v_dname departments.dept_name%type;
4 begin
5 select dept_id,dept_name into v_id,V_dname from departments where manager_id=200;
6 if v_id=11 then
7 dbms_output.put_line(v_dname);
8 elsif v_dname='cse' then
9 dbms_output.put_line(v_id);
10 else
11dbms_output.put_line('recorde not match');
12 end if;
13 end;
SQL> / 10
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PL/SQL procedure successfully completed.
3) if/else if/ else
1 declare
2 a number;
3 b number;
4 c number;
5 begin
6 a:=&a;
7 b:=&b;
8 c:=&c;
9 if (a>b) and (a>c) then
10 dbms_output.put_line('gratest number is'||a);
11 elsif(b>a) and (b>c) then
12 dbms_output.put_line('greatest number is'||b);
13 else
14 dbms_output.put_line('greatest number is'||c);
15 end if;
16 end;
SQL>/
Enter values for a,b and c: 6 4 12
C is greater :12.
Database Systems Lab Manual
PL/SQL procedure successfully completed.
4) Case Expressions
A case expression selects a result and returns it. To select the result, the case expression uses an expression whose value is used to select one of several alternatives.
Syntax :
CASE selector
WHEN
expression1
THEN result1 WHEN
expression2
THEN result2
---------
WHEN expression N THEN result N [ELSE resultN+1
END;
Example:
1 declare
2 va varchar2(10);
3 v_result varchar2(10);
4 begin
5 va:=&va;
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6 v_result:=
7 CASE va
8 WHEN 'a' THEN 'excellent'
9 WHEN 'b' THEN 'very good'
10 WHEN 'c' THEN 'good'
11 ELSE 'poor'
12 end;
13 dbms_output.put_line('grade is'||v_result);
14 end;
15 /
SQL> Enter value for va: 'a' old 5: va:=&va;
new 5: va:='a';
grade is excellent
PL/SQL procedure successfully completed.
SQL> /
Enter value for va: 'b' old 5: va:=&va;
new 5: va:='b';
grade is very good
PL/SQL procedure successfully completed.
SQL> /
Database Systems Lab Manual
Enter value for va: 'c' old 5: va:=&va;
new 5: va:='c';
grade is good
PL/SQL procedure successfully completed.
5) For Structure
SQL> 1 begin
2 for emp_record in (select * from wer1) loop
3 insert into wer1(name,ssn) values(emp_record.name,emp_record.ssn);
4 end loop;
5 commit;
6 end;
7 /
PL/SQL procedure successfully completed
Database Systems Lab Manual
CURSORS
The oracle server uses work areas, called private SQL areas, to execute SQL statement and to store processing information. This area is called cursor.
Cursor types:
 Implicit: queries returns only one row
 Explicit : queries returns more than one row
Explicit cursor
Active set: set of rows returned by multiple rows
Controlling explicit cursor
Open the cursor and execute the query associated with the cursor which identifies the result set.
Fetch
Retrieves the current row an advance the current row
Close the cursor
Syntax:
Cursor declaration
cursor cuname is select;
Open the cursor
open cursor name;
Close the cursor
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close cursor name;
Fetch
fetch cname into variable or record
Explicit Cursor Attributes: To determine the status of the cursor, the cursor’s attributes are checked.Cursors have the following four attributes that can be used in a PL/SQL program.
%isopen -To check if the cursor is opened or not
%found-To check if a record is found and can be fetched from the cursor
%rowcount-To check for the number of rows fetched from the cursor
%notfound-To check if no more records can be fetched from the cursor
%isopen, %found,%notfound are boolean attributes which are set to either TRUE or FALSE.
A Simple Example:
1 declare
2 v_name wer1.name%type;
3 v_ssn wer1.ssn%type;
4 cursor emp_c is select * from wer1;
5 begin
6 open emp_c;
7 for i in 1..5 loop
8 fetch emp_c into v_name,v_ssn;
9 dbms_output.put_line(v_name);
Database Systems Lab Manual
10 end loop;
11 close emp_c;
12 end;
PL/SQL procedure successfully completed.
SQL> set serveroutput on;
SQL> / x
x
x
y
y
2) %row count
1 declare
2 v_name wer1.name%type;
3 v_ssn wer1.ssn%type;
4 cursor emp_c is select * from wer1;
5 begin
6 open emp_c;
7 for i in 1..5 loop
8 fetch emp_c into v_name,v_ssn;
9 exit when emp_c%rowcount>4;
10 dbms_output.put_line(v_name);
Database Systems Lab Manual
11end loop;
12 close emp_c;
13 end;
SQL> / x
x
x
y
PL/SQL procedure successfully completed.
3) Cursor with record
It processes the rows of the active set by fetching values into a PL/SQL record.
1 declare
2 cursor emp_c is select * from wer1;
3 emp_record emp_c%rowtype;
4 begin
5 open emp_c;
6 for i in 1..5 loop
7 fetch emp_c into emp_record;
8 exit when emp_c%notfound;
9 insert into wer(name,ssn) values(emp_record.name,emp_re
10 end loop;
11 commit;
12 close emp_c;
Database Systems Lab Manual
13 end;
14 /
PL/SQL procedure successfully completed.
SQL> select * from wer;
NAME
SSN
----------
----------
x
101
x
101
x
101
x
101
x
101
x
101
x
101
x
101
x
101
x
101
y
102
y
102
12 rows selected.
4) Cursor with parameters
Database Systems Lab Manual
It passes the parameter values to the cursor in a cursor FOR loop. This means that you can open and close an explicit cursor several times in a block, returning a different active set on each occasion.
Example:
1 declare
2 v_number number;
3 v_name varchar2(10);
4 cursor c1(eno number,ename varchar2) is
5 select ssn,name from emp where ssn=eno and name=ename;
6 begin
7 open c1(101,'x');
8 fetch c1 into v_number,v_name;
9 dbms_output.put_line(v_number);
10 close c1;
11 open c1(102,'y');
12 fetch c1 into v_number,v_name;
13 dbms_output.put_line(v_number);
14 close c1;
15 end;
16 /
101
102
PL/SQL procedure successfully completed.
Database Systems Lab Manual
5) Update
The update clause in the cursor query locks the affected rows when the cursor is opened.
Example:
declare
v_number number;
v_name varchar2(10);
cursor c1(eno number,ename varchar2) is select ssn,name from emp where ssn=eno and
name=ename for update of name nowait;
begin
open c1(101,'x');
fetch c1 into v_number,v_name;
dbms_output.put_line(v_number);
close c1;
open c1(102,'y');
fetch c1 into v_number,v_name;
dbms_output.put_line(v_number);
close c1;
end;
EXCEPTIONS
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Syntax
When exception1
then Statement1
Statement2
……..
When exception2
then Statement1
Statement2
……..
When others
then Statement1
Statement2 ……..
Sample predefined exceptions:
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
ZERO_DIVIDE
DUP_VAL_ON_INDEX
Example:
1)
1 declare
Database Systems Lab Manual
2 a number;
3 b number;
4 c number;
5 begin
6 a:=5;
7 b:=0;
8 c:= a/b;
9 exception
10 when zero_divide then
11 dbms_output.put_line('zero divide error');
12 end;
SQL> /
zero divide error
PL/SQL procedure successfully completed.
2) Non-predefined error
Trapping a non-predefined exception
1. Declare the name for the exception within the declarative section
2. Associate the declared exception with the standard oracle server error number using the PRAGMA EXCEPTION_INIT statement
Syntax : PRAGMA EXCEPTION_INIT(exception, error_number);
3. Reference the declared exception within the corresponding exception –handling routine.
Database Systems Lab Manual
Example:
1 declare
2 emp_remain exception;
3 pragma exception_init
4 (emp_remain,-2292);
5 begin
6 delete from emp where deptno=&deptno;
7 commit;
8 exception
9 when emp_remain then
10 dbms_output.put_line('cannot remove dept'|| 'employee exist');
11end;
SQL> /
Enter value for deptno: 2
old 6: delete from emp where deptno=&deptno;
new 6: delete from emp where deptno=2;
cannot remove deptemployee exist
PL/SQL procedure successfully completed
SQL> /
Enter value for deptno: 8
old 6: delete from emp where deptno=&deptno;
Database Systems Lab Manual
new 6: delete from emp where deptno=8;
PL/SQL procedure successfully completed
3) Functions for trapping exceptions
When an exception occurs, you can identify the associated error code or error message by using two functions.
SQLCODE: It returns the numeric value for the error code
SQLERRM: It returns character data containing the message associated with the error number.
Syntax:
declare;
v_error_code number;
v_error_messgage varchar2(255);
begin
when others then rollback;
v_error_code:=sqlcode;
v_error_message:=sqlerrm;
dbms_output.put_line(v_error_code||v_error_message);
end;
User defined function:
User defined PL/SQL exception must be
Database Systems Lab Manual
• Declared in the declare section of a PL/SQL block
• Raised explicitly with RAISE statements
Example:
1 declare
2 invalid_dept exception;
3 begin
4 delete from emp where deptno=&deptno;
5 if sql%notfound then
6 raise invalid_dept;
7 end if;
8 exception
9 when invalid_dept then
10 dbms_output.put_line('the deptnumber is not valid');
11 end;
Enter value for deptno: 10
old 4: delete from emp where deptno=&deptno;
new 4: delete from emp where deptno=10;
the deptnumber is not valid
PL/SQL procedure successfully completed.
PL/SQL Block Types
A PL/SQL program comprises one or more blocks.
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It is classified into two blocks
 Anonymous Blocks
It is unnamed blocks. It is declared at the point in an application where they are to be executed and are passed to the PL/SQL engine for execution at run time.
 Subprograms
Subprograms are named PL/SQL blocks that can accept parameters and can be invoked. It can be declared either as procedures or as functions.
Overview of subprograms
A subprogram is named PL/SQL block that ca accept parameters and be invoked from a calling environment.
Two types of subprograms
 A procedure that performs an action
 A function that computes a value
Benefits of subprograms
 Easy maintenance
 Improved data security and integrity
 Improved performance
 Improved code clarity
Procedure
A procedure is a type of subprogram that performs an action. A procedure can be stored in the database, as a schema object, for repeated execution.
Database Systems Lab Manual
Syntax for creating procedure:
Create [or replace] procedure <procedure_name>
[( parameter1 [mode1] datatype1,parameter2 [mode2] datatype2,..)]
Is| As
PL/SQL Block;
The replace option indicates that if the procedure exists, It will be dropped and replaced with the new version created by the statement. Parameter name of a PL/SQL variable whose value is passed to or populated by the calling environment.
Mode: type of argument
IN, OUT, IN OUT
IN : It is the default mode and value is passed into subprogram.
OUT : It must be specified and is returned to calling environment.
IN OUT: It is passed into subprogram and returned to calling environment.
IN parameter
IN parameters are passed as constants from the calling environment into the procedure.
Example:1
1 create or replace procedure raise_salary
2 (grade in job_grade.gra%type)
Database Systems Lab Manual
3 is
4 begin
5 update job_grade set lowest_sal=lowest_sal*1.10 where gra= grade;
6* end raise_salary;
7 /
Procedure created.
SQL> execute raise_salary('a'); // executing procedure
PL/SQL procedure successfully completed.
SQL> select * from job_grade;
GRA LOWEST_SAL HIGHEST_SAL
---- ---------- -----------------------------------------
a 13200 4000
c 3000 6000
d 4000 10000
e 2000 6000
IN, OUT parameter
Example:1
Database Systems Lab Manual
1 create or replace procedure info
2 (g in job_grade.gra%type,
3 l_sal out job_grade.lowest_sal%type,
4 h_sal out job_grade.highest_sal%type)
5 is
6 begin
7 select lowest_sal,highest_sal into l_sal,h_sal from job_grade where gra=g;
8* end info;
9 /
SQL> edit g:\oracle\sql\info1.sql
SQL> @g:\oracle\sql\info1
Procedure created.
How to view the value of OUT parameters with sql *plus
1.Run the sql script file to generate and compile the source code.
2.Create host variables in sql*plus, using the variable command
3.Invoke the procedure, supplying these host variables as the OUT parameters.: reference the host variables in the execute command.
4.To view the values passed from the procedure to the calling environment ,use the print command.
SQL> variable g_sal number;
SQL> variable g1_sal number;
Database Systems Lab Manual
SQL> execute info('a',:g_sal,:g1_sal)
PL/SQL procedure successfully completed.
SQL> print g_sal;
G_SAL
----------
13200
SQL> print g1_sal;
G1_SAL
----------
4000
IN OUT parameter
Example:1
1 create or replace procedure info
2 (g in out number)
3 is
4 begin
5 select lowest_sal into g from job_grade where highest_sal=g;
6* end info;
7 /
Procedure created.
SQL> variable g_sal number;
1 begin
2 :g_sal:=4000;
Database Systems Lab Manual
3* end;
PL/SQL procedure successfully completed.
SQL> print g_sal;
G_SAL
----------
4000
SQL> execute info (:g_sal)
PL/SQL procedure successfully completed.
SQL> print g_sal;
G_SAL
----------
13200
Methods for passing parameters
Positional : List actual parameters in the same order as formal parameters
Named : List actual parameters in library order by associating each with its
corresponding formal parameter
Combination : List some of the actual parameters as positional and some as named.
Removing procedures
Drop a procedure stored in the database
Database Systems Lab Manual
Syntax:
Drop procedure procedure_name
Example:
Drop procedure raise_salary;
Functions
A function is a named PL/SQL block that returns a value. A function can be stored in the database as a schema object for repeated execution. A function is called as part of an expression.
Syntax:
Create [or replace] function function_name
[(parameter1 [mode1] datatype1,
Parameter2 [mode2] datatype2,
….)]
Return datatype
Is/as
PL/SQL block ;
Example:
declare
summation number;
Database Systems Lab Manual
average number;
function summa(m4 number,m5 number) return number is
begin
return(m4+m5);
end;
function aver( summ1 number) return number is
begin
return(summ1/2);
end;
begin
summation:=summa(&m1,&m2);
average:=aver(summation);
dbms_output.put_line('summation is:'||summation);
dbms_output.put_line('average is:'||average);
end;
Removing functions
Drop function function_name
Example:
Drop function summa;
Packages
Database Systems Lab Manual
Packages bundle are related PL/SQL types, items, and subprograms into one container.
A package usually has a specification and a body, stored separately in the database.
Package specification
It is the interface to the application. It declares the types, variables, constants, exceptions, cursors and subprograms.
A package specification can exist without a package body, but a package body cannot exist without a package specification.
Syntax
Create [or replace] package package_name
is| as
Public type and item declarations
Subprograms specifications
End package_name;
Example:
1 create or replace package commp is
2 g_comm number:=0.10;
3 procedure reset_comm
4 (p_comm in number);
5 end commp;
Package created.
Database Systems Lab Manual
Package body
Syntax
Create [or replace] package body package_name
Is| as
Private type and item declarations
Subprogram bodies
End package_name;
Example
1 create or replace package body commp
2 is
3 function validate_comm(p_comm in number)
4 return boolean
5 is
6 v_max_comm number;
7 begin
8 select max(lowest_sal) into v_max_comm from job_grade;
9 if p_comm>v_max_comm then return(false);
10 else return(true);
11 end if;
12 end validate_comm;
Database Systems Lab Manual
13 procedure reset_comm(p_comm in number)
14 is
15 begin
16 if validate_comm(p_comm)
17 then g_comm:=p_comm;
18 else
19 raise_application_error(-20210,'invalid commision');
20 end if;
21 end reset_comm;
22 end commp;
23 /
Package body created.
Invoking package constructs:
SQL> execute commp.reset_comm(0.15);
PL/SQL procedure successfully completed.
SQL> create or replace package global_con is
2 a constant number:=2;
3 b constant number :=3;
4 end global_con;
5 /
Package created.
SQL> execute dbms_output.put_line('20 miles='||20*global_con.a||'km');
Database Systems Lab Manual
20 miles=40km
PL/SQL procedure successfully completed.
Referencing a public variable from a stand alone procedure:
SQL> ed
Wrote file afiedt.buf
1 create or replace procedure me( x in number, y out number)
2 is
3 begin
4 y :=x *global_con.a;
5 end me;
SQL> /
Procedure created.
SQL> variable ya number;
SQL> execute me(3,:ya);
PL/SQL procedure successfully completed.
SQL> print ya;
YA
----------
6
Removing packages:
Database Systems Lab Manual
drop package package name;
drop package body package_name;
Overloading
It is the use of same name for different subprograms inside a PL/SQL block, a subprogram, or a package.
Example:
1 create or replace package over
2 is
3 procedure add_dept(p_n in emp.ssn%type,p_na in emp.name%type);
4 procedure add_dept(p_n in emp.ssn%type,p_na in emp.name%type,p_dept in emp.deptno%type);
5 end over;
6 /
Package created
1 create package body overp is
2 procedure add_dept(p_n emp.ssn%type,p_na emp.name%type)
3 is
4 begin
5 insert into emp (ssn,name) values(p_n,p_na);
6 end add_dept;
7 procedure add_dept(p_n emp.ssn%type,p_na emp.name%type,p_dn emp.deptno%type)
8 is
9 begin
10 insert into emp (ssn,name,deptno) values(p_n,p_na,p_dn);
Database Systems Lab Manual
11 end add_dept;
12 end overp;
Trigger
A trigger is aPL/SQL block or a PL/SQL procedure associated with a table ,view, schema, or the database. It executes implicitly whenever a particular event takes place.
It can be:
Application trigger: fires whenever an event occurs with a particular application
Database trigger: fires whenever a data event or system event occurs on a schema or database.
A triggering statement contains:
 Triggering timing
o For table: BEFORE, AFTER
o For view: INSTEAD OF
 Triggering event: INSERT, UPDATE, or DELETE
 Table name: on table, view
 Trigger type: row or statement
 When clause: restricting condition
 Trigger body: PL/SQL block
Trigger type
Statement trigger:The trigger body executes once for the triggering event. this is default. A statement trigger fires once, even if no rows are affected at all.
Row trigger:The trigger body executes once for each row affected by the triggering event. A
Database Systems Lab Manual
row trigger is not executed if the triggering event affects no rows.
Syntax:
CREATE [OR REPLACE] TRIGGER trigger_name
Timing
Event1 [OR event2 OR event3]
ON table_name
Trigger _body
Example:
create trigger ab
before insert or delete or update on a
for each row
begin
raise_application_error(-20000,'not accessible')
end
This program raises an error during insertion and deletion and update operation in a row.
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Database Systems Lab Manual