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;
[SQL]196. Delete Duplicate Emails
原文：http://www.cnblogs.com/fcyworld/p/6500965.html