What is the use of the MySQL NULLIF() control flow function?

The MySQL NULLIF() control flow function will return NULL if the two parameters are the same, otherwise it will return the first parameter.

Syntax

NULLIF(expression1, expression2)

Here, if expression1 = expression2, NULLIF() will return NULL, otherwise it will return expression1. The following example will demonstrate this -

mysql> Select NULLIF('Ram','Ram');
+---------------------+
| NULLIF('Ram','Ram') |
+---------------------+
| NULL                |
+---------------------+
1 row in set (0.00 sec)

mysql> Select NULLIF('Ram','Shyam');
+-----------------------+
| NULLIF('Ram','Shyam') |
+-----------------------+
| Ram                   |
+-----------------------+
1 row in set (0.00 sec)

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