What does the & lt;=> in mysql mean?
This article mainly explains "what does it mean in mysql". The content of the explanation in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what is meant in mysql".
In mysql, "" means "safe equal" and is a comparison operator, similar to the "=" equal operator, but "" can be used to determine the null value: when both operands are NULL, the return value is 1 instead of NULL;, and when an Operand is NULL, the return value is 0 instead of NULL.
The operating environment of this tutorial: windows7 system, mysql8 version, Dell G3 computer.
Security equals operator ()
The operator is similar to the = equals operator, but can be used to determine the NULL value. The specific syntax rules are:
When both operands are NULL, the return value is 1 instead of NULL
When an Operand is NULL, the return value is 0 instead of NULL.
Example: use to make an equal judgment
Mysql > SELECT 10, 2, 2, 22, 2, 0, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, (1, 3), (2, 1), NULLNULL. +-+ | 10 | '2percent 2 | 22 |' 0.02 percent 0 | 'bounded roomb' | (1: 3) (2: 1) | NULLNULL | +-- -+ | 0 | 1 | 1 | 0 | 1 | 0 | 1 | | +-+ 1 row in set (0.00 sec) |
As you can see from the results, the effects of = and = are similar when performing a comparison operation, except that they can be used to judge NULL. When both are NULL, the return value is 1.
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