Mysql开发技巧之删除重复数据

Mysql利用联表查询和分组来删除重复数据

//删除表中重复的id，保留最大的id
mysql> select * from user;
+----+------+
| id | name |
+----+------+
|   | a    |
|   | b    |
|   | c    |
|   | d    |
|   | a    |
|   | a    |
|   | c    |
|   | d    |
+----+------+
 rows in set (0.08 sec)

mysql> delete a from user a left join (select max(id) as id, name from user group by name having(count(id)) > )  b on a
.name = b.name where a.id < b.id;
Query OK,  rows affected (0.13 sec)

//删除重复数据成功
mysql> select * from user;
+----+------+
| id | name |
+----+------+
|   | b    |
|   | a    |
|   | c    |
|   | d    |
+----+------+