NULL-safe equal :<=> : NULL safe equal « Comparison Functions Operators « MySQL Tutorial

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MySQL Tutorial » Comparison Functions Operators » NULL safe equal

15. 14. 1. NULL-safe equal :<=>

NULL-safe equal(<=>) performs an equality comparison like the = operator.

NULL-safe equal(<=>) returns 1 rather than NULL if both operands are NULL.

NULL-safe equal(<=>) returns 0 rather than NULL if one operand is NULL.


mysql>

mysql> SELECT 1 <=> 1, NULL <=> NULL, 1 <=> NULL;

+---------+---------------+------------+

| 1 <=> 1 | NULL <=> NULL | 1 <=> NULL |

+---------+---------------+------------+

|       1 |             1 |          0 |

+---------+---------------+------------+

1 row in set (0.00 sec)



mysql>

mysql> SELECT 1 = 1, NULL = NULL, 1 = NULL;

+-------+-------------+----------+

| 1 = 1 | NULL = NULL | 1 = NULL |

+-------+-------------+----------+

|     1 |        NULL |     NULL |

+-------+-------------+----------+

1 row in set (0.00 sec)



mysql>

15. 14. NULL safe equal
	15. 14. 1.	NULL-safe equal :<=>

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