如何组合GROUP BY，ORDER BY和HAVING

Question

如何正确组合此声明。

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

让我知道

Answer 1

ORDER BY永远是最后的......

但是，您需要选择 ACTUALLY WANT 的字段，然后只选择那些并按其分组。 SELECT *和GROUP BY Email会为Email以外的所有字段提供 RANDOM VALUES 。大多数RDBMS甚至不允许你这样做，因为它创建的问题，但MySQL是例外。

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

Answer 2

您的代码应在WHILE和group by之前包含having：

SELECT Email, COUNT(*)

FROM user_log

WHILE Email IS NOT NULL

GROUP BY Email

HAVING COUNT(*) > 1

ORDER BY UpdateDate DESC

Answer 3

使用分组依据，按顺序排序......

Select Attitude ,count(*) from Person
group by person
HAving PersonAttitude='cool and friendly'
Order by PersonName.