ex 9
create or replace trigger delaccount
after delete on account
for each row
begin
if:old.balance >0 then
raise_application_error(-20001, 'You still have cash buddy');
rollback;
end if;
end;

delete from account where accountno =1;
insert into account values(5,1515151515, 0);
ZADANIE 15
select * from (
          select name,
                 salary,
                 dense_rank() over (order by salary desc) as rnk
          from person)
    where rnk <= 3 and rownum<=3;
ZADANIE 5
static void Insertexample()
            // inserts a new record in workplace
        {

            string cprstring;
            string companystring;
            Console.WriteLine("Indtast cpr-number");
            cprstring = Console.ReadLine();
            Console.WriteLine("Indtast company-number");
            companystring = Console.ReadLine();

            string sql;
            sql = "insert into workplace values ('"+ cprstring +  "'," + companystring + ")";
            //OracleCommand cmd = new OracleCommand();

            DbCommand cmd = dbFactory.CreateCommand();
            cmd.Connection = con;
            cmd.CommandText = sql;

            // lćs tabellen person
            try
            {   // ĺbn forbindelse til database
                con.Open();
                cmd.ExecuteNonQuery();
                Console.WriteLine("The insert is done");
            }
            catch (OracleException ex)
            {

                if (ex.Message.Contains("ORA-02291: integrity constraint (SYSTEM.CPRFOREIGN)"))
                    Console.WriteLine("The cpr number does not exits");
                if (ex.Message.Contains("ORA-02291: integrity constraint (SYSTEM.COMPANYFOREIGN)"))
                    Console.WriteLine("The company number does not exits");
                if(ex.Message.Contains("ORA-00001"))
                    Console.WriteLine("Person already exists in company");

            }

            finally
            {   // luk forbindelse til databasen
                con.Close();
            }

            Console.WriteLine();
            Console.WriteLine("---------------------------------------------------------------------");
        }