Comparison Operators

Operator

Purpose

Example

=

Equality test

SELECT * FROM DEPARTMENT

WHERE Fund = 15000;

!=, ^=, <>, ¬=

Inequality test.

SELECT * FROM DEPARTMENT

WHERE Fund != 15000;

>, <

"Greater than" and "less than" tests

SELECT * FROM FACULTY SELECT * FROM FACULTY

WHERE Fund > 1500; WHERE Fund < 1500;

>=, <=

"Greater than or equal to" and "less than or equal to" tests

SELECT * FROM FACULTY SELECT * FROM FACULTY

WHERE Fund >= 1500; WHERE Fund <= 1500;

IN

"Equal to any member of" test. Equivalent to "= ANY"

SELECT Name, Post FROM TEACHER WHERE Post IN ('professor', 'assistant');

NOT IN

Equivalent to !=ALL. Evaluates to FALSE if any member of the set is NULL

SELECT * FROM FACULTY

WHERE Fund NOT IN

(SELECT Fund FROM FACULTY WHERE Building IN ('3','5')};

ANY, SOME

Compares a value to each value in a list or returned by a query. Must be preceded by =, !=, >, <, <=, >=. Evaluates to FALSE if the query returns no rows.

SELECT * FROM TEACHER

WHERE Salary = ANY

(SELECT Salary FROM TEACHER

WHERE Post = 'professor');

ALL

Compares a value to every value in a list or returned by a query. Must be preceded by =, !=, >, <, <=, >=. Evaluates to TRUE if the query returns no rows.

SELECT * FROM TEACHER

WHERE Salary >= ALL (350, 400, 420);

[NOT] BETWEEN x AND y

[Not] greater than or equal to x and less than or equal to y.

SELECT * FROM TEACHER

WHERE Salary BETWEEN 350 AND 420;

EXISTS

TRUE if a subquery returns at least one row. It is unary operator.

SELECT Name FROM TEACHER

WHERE EXISTS

(SELECT * FROM LECTURE

WHERE LECTURE.TchNo=TEACHER. TchNo);

x [NOT] LIKE y [ESCAPE ‘z’]

TRUE if x does [not] match the pattern y. Within y, the character "%" matches any string of zero or more characters except null. The character "_" matches any single character. Any character, excepting percent (%) and underbar (_) may follow ESCAPE. A wildcard character is treated as a literal if preceded by the character designated as the escape character.

SELECT Name FROM TEACHER

WHERE Name LIKE 'Ив%';

IS [NOT] NULL

Tests for nulls. This is the only operator that you should use to test for nulls.

SELECT Name, Tel

FROM TEACHER

WHERE Commission IS NULL;

Operator

Purpose

Example

NOT

Unary operator. Returns TRUE if the condition is FALSE. Returns FALSE if it is TRUE. If it isUNKNOWN, it remainsUNKNOWN.

SELECT * FROM TEACHER

WHERE NOT (Salary BETWEEN 450 AND 500);

AND

Binary operator. Returns TRUE if both com­po­nent conditions are TRUE. Returns FALSE if either is FALSE. Otherwise returnsUNKNOWN.

SELECT * FROM TEACHER

WHERE Hiredate < TO_DATE('01-JAN-2000', 'DD-MMM-YYYY') AND Salary > 500;

OR

Binary operator. Returns TRUE if either component condition is TRUE. Returns FALSE if both are FALSE. Otherwise returnsUNKNOWN.

SELECT *

FROM TEACHER

WHERE Post = 'assistant' AND

Salary > 500;