leetcode数据库sql之Delete Duplicate Emails

leetcode原文引用：

Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id.

+----+------------------+
| Id | Email            |
+----+------------------+
| 1  | john@example.com |
| 2  | bob@example.com  |
| 3  | john@example.com |
+----+------------------+
Id is the primary key column for this table.

For example, after running your query, the above Person table should have the following rows:

+----+------------------+
| Id | Email            |
+----+------------------+
| 1  | john@example.com |
| 2  | bob@example.com  |
+----+------------------+

DELETE FROM Person 
WHERE
    id NOT IN (SELECT 
        id
    FROM
        (SELECT 
            MIN(id) AS id
        FROM
            Person
        GROUP BY email) AS a);

leetcode数据库sql之Delete Duplicate Emails

原文：http://blog.csdn.net/zkn_cs_dn_2013/article/details/47304413