196. Delete Duplicate Emails (Easy)

Source: https://leetcode.com/problems/delete-duplicate-emails/#/description
Description:

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 |
+----+------------------+

 

Solution:

delete from 
Person
where  
Id not in (select Id from 
            (select min(Id) as Id 
                from Person 
                group by Email
            ) p
          );
posted @ 2017-05-21 15:08  sixu  阅读(162)  评论(0)  编辑  收藏  举报