标签：一个 pre 条件 rom select 使用 标准 style 将不
编写一个 SQL 查询，查找 Person 表中所有重复的电子邮箱。
示例： +----+---------+ | Id | Email | +----+---------+ | 1 | a@b.com | | 2 | c@d.com | | 3 | a@b.com | +----+---------+ 根据以上输入，你的查询应返回以下结果： +---------+ | Email | +---------+ | a@b.com | +---------+ 说明：所有电子邮箱都是小写字母。
`解题思路`
1 嵌套表查询
`select Email from ( select Email, count(Email) as a from Person group by Email) as b where a>1`
2 group by ... having
`select Email from Person group by Email having count(Email) > 1;`
标签：一个 pre 条件 rom select 使用 标准 style 将不
原文地址：https://www.cnblogs.com/8013-cmf/p/12529915.html
