IS NULL
IS NULL
is used to test if an expression is null.
Syntax
expr IS [ NOT ] NULL
Arguments
Parameter |
Description |
---|---|
|
A general value expression or a literal to test. |
Returns
Returns TRUE
when expr
is NULL
or FALSE
otherwise.
Examples
For these examples, consider the following table and contents:
CREATE TABLE t (id INT NOT NULL, name TEXT(30), weight INT);
INSERT INTO t VALUES (1, 'Kangaroo', 120), (2, 'Koala', 20), (3, 'Wombat', 60)
,(4, 'Kappa', NULL),(5, 'Echidna', 8),(6, 'Chupacabra', NULL)
,(7, 'Kraken', NULL);
IS NULL
m=> SELECT * FROM t WHERE weight IS NULL;
id | name | weight
---+------------+-------
4 | Kappa |
6 | Chupacabra |
7 | Kraken |
Using IS NOT NULL to filter unwanted results
m=> SELECT AVG(weight) FROM t WHERE weight IS NOT NULL;
avg
---
52