MySql:是否可以'SUM IF'或'COUNT IF'? [英] MySql: is it possible to 'SUM IF' or to 'COUNT IF'?

问题描述

我有一个小时"列 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...是什么错误！?

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

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

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

..我无法回复此...

.. 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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