"="和“< =>"之间是否存在性能差异?

问题描述：

我最近将所有where条件更改为使用<=>而不是=，因为我需要检查是否为空.有性能方面的问题吗?

I've recently changed all my where conditions to use <=> instead of = because I need to check against nulls. Are there any performance concerns?

答

这对性能没有实际影响，这是一个可以自己验证的测试

There is no real performance impact here is a test to verify for yourself

mysql> SELECT BENCHMARK(1000000, (SELECT SQL_NO_CACHE userId FROM Activity WHERE userId<=>42459204 LIMIT 1));

确保您需要使用< =>

Make sure that you need to use <=>

NULL安全等于.这个运算符执行像这样的相等比较 =运算子，但传回1 如果两个操作数均为NULL，则返回NULL，如果一个操作数，则返回0而不是NULL 是NULL.

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.

如果只需要检查右值，就可以

If you just need to check the rvalue do

col = CONST并且CONST不为空

col=CONST AND CONST IS NOT NULL

或t1.col = t2.col

or t1.col=t2.col

"="和“< =>"之间是否存在性能差异?

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