MySql:是否可以“SUM IF"或“COUNT IF"?

问题描述

我有一列小时"我有一列种类"(可以是 1,2 或 3)

I have a column 'hour' I have a column 'kind' (it can be 1,2 or 3)

我想做类似的事情:

SELECT count(id), SUM(hour) as totHour, SUM( IF ( kind = 1, 1, 0 ) ) as countKindOne

或

SELECT count(id), SUM(hour) as totHour, COUNT( IF ( kind = 1 ) ) as countKindOne

但是 mysql 告诉我我有一个错误...错误是什么！?

But mysql tell me I've an error... what's the error!?

请参阅此 stackoverflow 主题:MySQL SUM IF 字段 b = 字段 a

Please see this stackoverflow topic: MySQL SUM IF field b = field a

...我无法回复这个...

.. I'm not able to reply this ...

推荐答案

您可以使用 CASE 语句:

SELECT count(id), 
    SUM(hour) as totHour, 
    SUM(case when kind = 1 then 1 else 0 end) as countKindOne

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