The logical operators combine the results of two component conditions to produce a single result.

The logical operators provide by oracle are

• Logical Conjunction Operator - AND
• Logical Disjunction Operator - OR
• Logical Negation Operator - NOT

AND Operator :

• It returns TRUE if both or all component conditions are TRUE.
• It returns FALSE if either is FALSE, else returns unknown.
  

Truth table :

AND	TRUE	FALSE	NULL
TRUE	T	F	NULL
FALSE	F	F	F
NULL	NULL	F	NULL

Examples :

1.

SELECT Ename, Sal, Deptno, Job

FROM Emp

WHERE Deptno=20 AND Job='MANAGER';

2.

SELECT Empno, Ename, Sal, Job

FROM Emp

WHERE Sal>=1100 AND Job='CLERK';

3.

SELECT Ename, Sal, Job

FROM Emp

WHERE Sal>=1500 AND Sal>5000;

4.

SELECT Ename, Sal, Job

FROM Emp

WHERE Deptno=10 AND Job='CLERK';

5.

SELECT Ename, Sal, Job

FROM Emp

WHERE ( Sal>=1500 AND Sal<=5000) AND Job='MANAGER';

OR Operator :

• It returns TRUE if either of the component condition is true.
• It returns FALSE if both are FALSE, else returns unknown.

Truth table :

OR	TRUE	FALSE	NULL
TRUE	T	T	T
FALSE	T	F	NULL
NULL	T	NULL	NULL

Examples :

1.

SELECT Ename, Sal, Deptno, Job

FROM Emp

WHERE Deptno=20 OR Job='MANAGER';

2.

SELECT Empno, Ename, Sal, Job

FROM Emp

WHERE Sal>=1100 OR Job='CLERK';

3.

SELECT Ename, Sal, Job

FROM Emp

WHERE Sal>=1500 OR Sal>5000;

4.

SELECT Ename, Sal, Job

FROM Emp

WHERE Deptno=10 OR Deptno=20;

5.

SELECT Ename, Sal, Job

FROM Emp

WHERE ( Sal>=1500 OR Sal<=5000) OR Job='MANAGER';

6.

SELECT Ename, Sal, Deptno, Job

FROM Emp

WHERE Job='CLERK' OR Job='MANAGER';

NOT Operator :

• It returns TRUE if the following condition is FALSE.
• It returns FALSE if the following condition is TRUE.
• If the condition is unknown, it returns unknown.

Truth table :

NOT	TRUE	FALSE	NULL
NOT	F	F	NULL

Examples :

1.

SELECT Ename, Sal, Job

FROM Emp

WHERE NOT Job='MANAGER';

2.

SELECT Ename, Sal, Hiredate

FROM Emp

WHERE NOT Hiredate='20-FEB-81';

3.

SELECT Ename, Sal, Job

FROM Emp

WHERE NOT Sal>5000;

4.

SELECT Ename, Sal, Job,Deptno

FROM Emp

WHERE NOT Job='SALESMAN' AND Deptno=30;