Reputation: 31263
What is the MySQL <=>?
Because the operator is a symbol it is hard to look for documentation. (Similar to the ternary operator ?: for programing languages that support them.)
I got it from an example in a book.
mysql> select null <=> null;
+---------------+
| null <=> null |
+---------------+
| 1 |
+---------------+
1 row in set (0.00 sec)
Upvotes: 4
Views: 258
Reputation: 642
http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html#operator_equal-to
NULL-safe equal. This operator performs an equality comparison like the = operator, but returns 1 rather than NULL if both operands are NULL, and 0 rather than NULL if one operand is NULL.
Upvotes: 0
Reputation: 201
NULL-safe equal. This operator performs an equality comparison like the = operator, but returns 1 rather than NULL if both operands are NULL, and 0 rather than NULL if one operand is NULL.
http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html#operator_equal-to
Upvotes: 3
Reputation: 283355
It's a null-safe comparison operator. And it's awesome.
What that means is if you're trying to query your database for some variable, like a string, that might sometimes be null, you want to use it. For example, if you try searching SELECT * FROM table WHERE x = NULL
it will return nothing, but if you do SELECT * FROM table WHERE x <=> NULL
it'll work.
Upvotes: 6