MySql-在哪里 [英] MySql - HAVING vs WHERE

问题描述

这两个查询有什么区别?

What is the difference between these 2 queries?

SELECT f.name, 
       u.name, 
       u.id 
FROM   families f 
       JOIN units u 
         ON f.unit_id = u.id 
HAVING u.id IN( 43, 413, 22 )

并且:

SELECT f.name, 
       u.name, 
       u.id 
FROM   families f 
       JOIN units u 
         ON f.unit_id = u.id 
WHERE  u.id IN( 43, 413, 22 )

这两个查询的结果完全相同.那有什么区别呢?

The result of these 2 queries is exactly the same. So where is the difference?

推荐答案

sql中的having和where子句之间的区别是where子句不能与聚合一起使用，但是having子句可以使用.一种考虑方式是，having子句是where子句的附加过滤器.

Difference between the having and where clause in sql is that the where clause can not be used with aggregates, but the having clause can. One way to think of it is that the having clause is an additional filter to the where clause.

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