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NULLIF

The NULLIF() function compares two expressions and returns NULL if they are equal. Otherwise, the first expression is returned.

tip

Before using this function, you must enable the new Databend planner. To do so, perform the following command in the SQL client:

> set enable_planner_v2=1;

Syntax​

IF( <expr1>, <expr2>)

Arguments​

ArgumentsDescription
<expr1>Any general expression of any data type.
<expr2>Any general expression that evaluates to the same data type as \<expr1>.

Return Type​

The data type of the returned value is the data type of \<expr1>.

Examples​

SET enable_planner_v2 = 1;

SELECT a, b, NULLIF(a, b) FROM t;
+------+------+--------------+
| a    | b    | NULLIF(a, b) |
+------+------+--------------+
|    0 |    0 |         NULL |
|    0 |    1 |            0 |
|    0 | NULL |            0 |
|    1 |    0 |            1 |
|    1 |    1 |         NULL |
|    1 | NULL |            1 |
| NULL |    0 |         NULL |
| NULL |    1 |         NULL |
| NULL | NULL |         NULL |
+------+------+--------------+