如何结合GROUP BY，ORDER BY和HAVING [英] How to combine GROUP BY, ORDER BY and HAVING

问题描述

如何正确组合此语句.

SELECT *, COUNT(*)
FROM user_log
GROUP BY Email
ORDER BY UpdateDate DESC
HAVING COUNT(*) > 1

让我知道

推荐答案

ORDER BY永远是最后一个...

ORDER BY is always last...

但是，您需要选择要完全想要的字段，然后仅选择这些字段并按其分组.对于Email以外的所有字段，SELECT *和GROUP BY Email将为您提供 RANDOM VALUES .大多数RDBMS甚至会由于其创建的问题而不允许您执行此操作，但是MySQL是例外.

However, you need to pick the fields you ACTUALLY WANT then select only those and group by them. SELECT * and GROUP BY Email will give you RANDOM VALUES for all the fields but Email. Most RDBMS will not even allow you to do this because of the issues it creates, but MySQL is the exception.

SELECT Email, COUNT(*)
FROM user_log
GROUP BY Email
HAVING COUNT(*) > 1
ORDER BY UpdateDate DESC

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