MySQL的count(1)和count(*)和count(列名)的区别

Posted on 2020-03-01 In sql Valine:
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count(*)会统计为null的字段，count(1)和count(列名)不会统计该列为null的字段

查询速度count(主键)>count(1)>count(*)

distinct count(*)返回不重复且不含null的值