有关mysql删除重复记录的方法，我在网上看到很多文章，很多是照抄的，我自己按网上的方法实验了一下，没有一个sql语句就能解决的方法，不知道有没有高手可以出招。
我试验的过程如下：
?
mysql> select * from duplicate;
+----+-------+
| id | name? |
+----+-------+
|? 1 | wang? |
|? 2 | wang? |
|? 3 | wdang |
|? 4 | wdang |
|? 5 | wdand |
|? 6 | wddda |
+----+-------+
6 rows in set (0.00 sec)
select * from duplicate where id in(select min(id) from duplicate group by name);
+----+-------+
| id | name? |
+----+-------+
|? 1 | wang? |
|? 3 | wdang |
|? 5 | wdand |
|? 6 | wddda |
+----+-------+
4 rows in set (0.01 sec)
mysql> delete from duplicate where id not in(select min(id) from duplicate group by name);
ERROR 1093 (HY000): You can't specify target table 'duplicate' for update in FROM clause
?
最后我用了笨办法，复制无重复记录到新表格，删除旧表格，然后重命名新表格为旧表名称。
?
mysql> select * from duplicate where id in(select min(id) from duplicate group by name);
+----+-------+
| id | name? |
+----+-------+
|? 1 | wang? |
|? 3 | wdang |
|? 5 | wdand |
|? 6 | wddda |
+----+-------+
4 rows in set (0.01 sec)
mysql> create table duplica select * from duplicate where id in(select min(id) from duplicate group by name);
Query OK, 4 rows affected (0.02 sec)
Records: 4? Duplicates: 0? Warnings: 0
mysql> drop table duplicate;
Query OK, 0 rows affected (0.01 sec)
mysql> alter table duplica rename to duplicate;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from duplicate;
+----+-------+
| id | name? |
+----+-------+
|? 1 | wang? |
|? 3 | wdang |
|? 5 | wdand |
|? 6 | wddda |
+----+-------+
4 rows in set (0.00 sec)
?
mysql> alter table duplicate modify id int(2) not null primary key auto_increment;
Query OK, 4 rows affected (0.00 sec)
Records: 4? Duplicates: 0? Warnings: 0
?
?
后来想了一个语句搞定了：
mysql> use mysql
Database changed
mysql> select * from duplicate;
+----+-------+
| id | name? |
+----+-------+
|? 1 | wang? |
|? 3 | wdang |
|? 5 | wdand |
|? 6 | wddda |
|? 2 | wang? |
|? 4 | wdang |
+----+-------+
6 rows in set (0.00 sec)
mysql> delete duplicate as a from duplicate as a,
??? -> (
??? -> select * from duplicate group by name having count(1)>1) as b
??? -> where a.name=b.name and a.id > b.id;
Query OK, 2 rows affected (0.00 sec)
mysql> select * from duplicate;
+----+-------+
| id | name? |
+----+-------+
|? 1 | wang? |
|? 3 | wdang |
|? 5 | wdand |
|? 6 | wddda |
+----+-------+
4 rows in set (0.00 sec)
文章出处：飞诺网(www.firnow.com):http://dev.firnow.com/course/7_databases/mysql/Mysqljs/20100710/399218.html