MySQL 中查找重复数据，删除重复数据

数据库版本 Server version: 5.1.41-community-log MySQL Community Server (GPL)

例1，表中有主键(可唯一标识的字段)，且该字段为数字类型

删除重复数据，只保留一条数据

/* 删除重复数据，只保留一条数据 */
DELETE FROM `noid`
USING `noid`,(
SELECT DISTINCT MIN(`id`) AS `id`,`name`,`add`
FROM `noid`
GROUP BY `name`,`add`
HAVING COUNT(1) > 1
) AS `t2`
WHERE `noid`.`name` = `t2`.`name`
AND `noid`.`add` = `t2`.`add`
AND `noid`.`id` <> `t2`.`id`;
Query OK, 8 rows affected (0.05 sec)

/* 删除id字段 */
ALTER TABLE `noid` DROP `id`;
Query OK, 15 rows affected (0.16 sec)
Records: 15  Duplicates: 0  Warnings: 0

SELECT * FROM `noid`;
+----+------+-----+
| pk | name | add |
+----+------+-----+
| a  | abc  | 123 |
| c  | abc  | 321 |
| e  | xzy  | 123 |
| f  | xzy  | 456 |
| i  | xzy  | 789 |
| j  | xzy  | 987 |
| l  | ijk  | 147 |
| n  | ijk  | 852 |
| o  | opq  | 852 |
| p  | opq  | 963 |
| q  | opq  | 741 |
| r  | tpk  | 741 |
| s  | tpk  | 963 |
| u  | wer  | 546 |
| w  | once | 546 |
+----+------+-----+
15 rows in set (0.00 sec)