What does <=> mean in mysql

In mysql, "<=>" means "safe equal". It is a comparison operator, similar to the "=" equal operator, but "<=>" can be used To judge the NULL value: when both operands are NULL, the return value is 1 instead of NULL; and when one operand is NULL, the return value is 0 instead of NULL.

The operating environment of this tutorial: windows7 system, mysql8 version, Dell G3 computer.

Safe equals operator (<span style="font-size: 18px;"><=></span>)

<=> operator is similar to the = equals operator, but <=> can be used to determine NULL values, specific syntax The rules are:

• When both operands are NULL, the return value is 1 instead of NULL;

• And when a When the operand is NULL, the return value is 0 instead of NULL.

##Example: Use <=> to make an equal judgment

mysql> SELECT 1<=>0,&#39;2&#39;<=>2,2<=>2,&#39;0.02&#39;<=>0,&#39;b&#39;<=>&#39;b&#39;,(1+3) <=> (2+1),NULL<=>NULL;
+-------+---------+-------+------------+-----------+-----------------+-------------+
| 1<=>0 | &#39;2&#39;<=>2 | 2<=>2 | &#39;0.02&#39;<=>0 | &#39;b&#39;<=>&#39;b&#39; | (1+3) <=> (2+1) | NULL<=>NULL |
+-------+---------+-------+------------+-----------+-----------------+-------------+
|     0 |       1 |     1 |          0 |         1 |               0 |           1 |
+-------+---------+-------+------------+-----------+-----------------+-------------+
1 row in set (0.00 sec)

<=> ; has a similar function to = when performing comparison operations. The only difference is that <=> can be used to judge NULL, both of which are The return value is 1 when NULL.

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