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


# Write your MySQL query statement below
DELETE p from Person p, Person q where p.Id>q.Id AND q.Email=p.Email 

 

posted on 2015-07-07 22:25  风云逸  阅读(72)  评论(0)    收藏  举报