AND Operator#

In PostgreSQL, a boolean value can have one of three values: true, false, and null.

	Result
true	true
t	true
‘true’	true
‘y’	true
‘yes’	true
‘1’	true
false	false
f	false
‘false’	false
‘n’	false
‘no’	false
‘0’	false

A boolean expression is an expression that evaluates to a boolean value. For example, the expression 1=1 is a boolean expression that evaluates to true

SELECT 1 = 1 AS result;

 result 
--------
 t
(1 row)

The letter t in the output indicates the value of true. The AND operator is a logical operator that combines two boolean expressions.

Basic PostgreSQL AND operator examples#

The following example uses the AND operator to combine two true values, which returns true

SELECT true AND true AS result;

result
--------
 t
(1 row)

The following statement uses the AND operator to combine true with false, which returns false

SELECT true AND false AS result;

result
--------
 f
(1 row)

The following example uses the AND operator to combine true with null, which returns null

SELECT true AND null AS result;

result
--------
 null
(1 row)

The following example uses the AND operator to combine false with false, which returns false

SELECT false AND false AS result;

result
--------
 f
(1 row)

The following example uses the AND operator to combine false with null, which returns false

SELECT false AND null AS result;

result
--------
 f
(1 row)

Using the AND operator in the WHERE clause#

The following example uses the AND operator in the WHERE clause to find the films that have a length greater than 180 and a rental rate less than 1.

SELECT
  title,
  length,
  rental_rate
FROM
  film
WHERE
  length > 180
  AND rental_rate < 1;

title        | length | rental_rate
--------------------+--------+-------------
 Catch Amistad      |    183 |        0.99
 Haunting Pianist   |    181 |        0.99
 Intrigue Worst     |    181 |        0.99
 Love Suicides      |    181 |        0.99
 Runaway Tenenbaums |    181 |        0.99
 Smoochy Control    |    184 |        0.99
 Sorority Queen     |    184 |        0.99
 Theory Mermaid     |    184 |        0.99
 Wild Apollo        |    181 |        0.99
 Young Language     |    183 |        0.99
(10 rows)