SQL> select * from (select ename, job, sal, deptno from emp where deptno=20) union (select ename, job, sal, deptno from emp where sal=1250 );

ENAME      JOB              SAL     DEPTNO
---------- --------- ---------- ----------
ADAMS      CLERK           1100         20
FORD       ANALYST         3000         20
JONES      MANAGER         2975         20
MARTIN     SALESMAN        1250         30
SCOTT      ANALYST         3000         20
SMITH      CLERK            800         20
WARD       SALESMAN        1250         30

7 rows selected.

SQL> spool off





SQL> select ename from emp union select dname from dept;

ENAME
--------------
ACCOUNTING
ADAMS
ALLEN
BLAKE
CLARK
FORD
JAMES
JONES
KING
MARTIN
MILLER

ENAME
--------------
OPERATIONS
RESEARCH
SALES
SCOTT
SMITH
TURNER
WARD

18 rows selected.

SQL> spool off





SQL> select ename, job, sal, comm from emp where job='SALESMAN' and ((not comm>0 )or (comm is null));

ENAME      JOB              SAL       COMM
---------- --------- ---------- ----------
TURNER     SALESMAN        1500          0

SQL> spool off










SQL> (select ename, job, sal, comm from emp where job='SALESMAN' ) intersect (select ename, job, sal, comm from emp where (not comm > 0) or (comm is null));

ENAME      JOB              SAL       COMM
---------- --------- ---------- ----------
TURNER     SALESMAN        1500          0

SQL> spool off