表结构： mysql> desc demo; +-------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+------------------+------+-----+---------+----------------+ | id | int(11) unsigned | NO | PRI | NULL | auto_increment | | site | varchar(100) | NO | MUL | | | +-------+------------------+------+-----+---------+----------------+ 2 rows in set (0.00 sec) 数据： mysql> select * from demo order by id; +----+------------------------+ | id | site | +----+------------------------+ | 1 | http://www.CodeBit.cn | | 2 | http://YITU.org | | 3 | http://www.ShuoWen.org | | 4 | http://www.CodeBit.cn | | 5 | http://www.ShuoWen.org | +----+------------------------+ 5 rows in set (0.00 sec) [h1]当没有创建表或创建索引权限的时候，可以用下面的方法：[/h1] 如果你要删除较旧的重复记录，可以使用下面的语句： mysql> delete from a -> using demo as a, demo as b -> where (a.id > b.id) -> and (a.site = b.site); Query OK, 2 rows affected (0.12 sec) mysql> select * from demo order by id; +----+------------------------+ | id | site | +----+------------------------+ | 1 | http://www.CodeBit.cn | | 2 | http://YITU.org | | 3 | http://www.ShuoWen.org | +----+------------------------+ 3 rows in set (0.00 sec) 如果你要删除较新的重复记录，可以使用下面的语句： mysql> delete from a -> using demo as a, demo as b -> where (a.id < b.id) -> and (a.site = b.site); Query OK, 2 rows affected (0.12 sec) mysql> select * from demo order by id; +----+------------------------+ | id | site | +----+------------------------+ | 2 | http://YITU.org | | 4 | http://www.CodeBit.cn | | 5 | http://www.ShuoWen.org | +----+------------------------+ 3 rows in set (0.00 sec) 你可以用下面的语句先确认将被删除的重复记录： mysql> SELECT a.* -> FROM demo a, demo b -> WHERE a.id > b.id -> AND (a.site = b.site); +----+------------------------+ | id | site | +----+------------------------+ | 1 | http://www.CodeBit.cn | | 3 | http://www.ShuoWen.org | +----+------------------------+ 2 rows in set (0.00 sec) [h1]如果有创建索引的权限，可以用下面的方法：[/h1] 在表上创建唯一键索引：

 
mysql> alter ignore table demo add unique index ukey (site); 
Query OK, 5 rows affected (0.46 sec) 
Records: 5 Duplicates: 2 Warnings: 0 

mysql> select * from demo order by id; 
+----+------------------------+ 
| id | site | 
+----+------------------------+ 
| 1 | http://www.CodeBit.cn | 
| 2 | http://YITU.org | 
| 3 | http://www.ShuoWen.org | 
+----+------------------------+ 
3 rows in set (0.00 sec) 

重复记录被删除后，如果需要，可以删除索引：

 
mysql> alter table demo drop index ukey; 
Query OK, 3 rows affected (0.37 sec) 
Records: 3 Duplicates: 0 Warnings: 0 

[h1]如果有创建表的权限，可以用下面的方法：[/h1] 创建一个新表，然后将原表中不重复的数据插入新表：

 
mysql> create table demo_new as select * from demo group by site; 
Query OK, 3 rows affected (0.19 sec) 
Records: 3 Duplicates: 0 Warnings: 0 

mysql> show tables; 
+----------------+ 
| Tables_in_test | 
+----------------+ 
| demo | 
| demo_new | 
+----------------+ 
2 rows in set (0.00 sec) 

mysql> select * from demo order by id; 
+----+------------------------+ 
| id | site | 
+----+------------------------+ 
| 1 | http://www.CodeBit.cn | 
| 2 | http://YITU.org | 
| 3 | http://www.ShuoWen.org | 
| 4 | http://www.CodeBit.cn | 
| 5 | http://www.ShuoWen.org | 
+----+------------------------+ 
5 rows in set (0.00 sec) 

mysql> select * from demo_new order by id; 
+----+------------------------+ 
| id | site | 
+----+------------------------+ 
| 1 | http://www.CodeBit.cn | 
| 2 | http://YITU.org | 
| 3 | http://www.ShuoWen.org | 
+----+------------------------+ 
3 rows in set (0.00 sec) 

然后将原表备份，将新表重命名为当前表：

 
mysql> rename table demo to demo_old, demo_new to demo; 
Query OK, 0 rows affected (0.04 sec) 

mysql> show tables; 
+----------------+ 
| Tables_in_test | 
+----------------+ 
| demo | 
| demo_old | 
+----------------+ 
2 rows in set (0.00 sec) 

mysql> select * from demo order by id; 
+----+------------------------+ 
| id | site | 
+----+------------------------+ 
| 1 | http://www.CodeBit.cn | 
| 2 | http://YITU.org | 
| 3 | http://www.ShuoWen.org | 
+----+------------------------+ 
3 rows in set (0.00 sec) 

[b]注意：使用这种方式创建的表会丢失原表的索引信息！[/b]

 
mysql> desc demo; 
+-------+------------------+------+-----+---------+-------+ 
| Field | Type | Null | Key | Default | Extra | 
+-------+------------------+------+-----+---------+-------+ 
| id | int(11) unsigned | NO | | 0 | | 
| site | varchar(100) | NO | | | | 
+-------+------------------+------+-----+---------+-------+ 
2 rows in set (0.00 sec) 

如果要保持和原表信息一致，你可以使用 show create table demo; 来查看原表的创建语句，然后使用原表的创建语句创建新表，接着使用 insert … select 语句插入数据，再重命名表即可。 当然，如果要避免重复记录，最好的办法还是不要插入重复数据，可以参考本站另外一篇文章：[url=http://www.1sucai.cn/article/15627.htm]MySQL 当记录不存在时插入[/url]