[SQL]196. Delete Duplicate Emails

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

1 # Write your MySQL query statement below
2 delete p1
3 from Person p1,Person p2
4 where p1.Email=p2.Email
5 and p1.Id>p2.Id;

 

转载于:https://www.cnblogs.com/fcyworld/p/6500965.html