mysql 中如何删除重复的数据_mysql如何快速删除重复的数据_MySQL

在mysql中去重，其实是一个很简单的事情，来看下面的例子：

mysql> DROP TABLE test;

Query OK, 0 rows affected (0.01 sec)

mysql> CREATE TABLE test

(

id INT,

NAME VARCHAR(10)

);

Query OK, 0 rows affected (0.01 sec)

mysql> INSERT INTO test VALUES(1,'a1'),(2,'a2'),(3,'a3'),(4,'a4'),(1,'a1');

Query OK, 5 rows affected (0.00 sec)

Records: 5 Duplicates: 0 Warnings: 0

mysql> SELECT * FROM test;

+------+------+

| id | NAME |

+------+------+

| 1 | a1 |

| 2 | a2 |

| 3 | a3 |

| 4 | a4 |

| 1 | a1 |

+------+------+

5 rows in set (0.00 sec)

mysql> ALTER IGNORE TABLE test ADD UNIQUE INDEX idx_id_name (id,NAME);

Query OK, 5 rows affected, 1 warning (0.02 sec)

Records: 5 Duplicates: 1 Warnings: 1

mysql> SHOW WARNINGS;

+---------+------+-----------------------------------------------------------------+

| Level | Code | Message |

+---------+------+-----------------------------------------------------------------+

| Warning | 1681 | 'IGNORE' is deprecated and will be removed in a future release. |

+---------+------+-----------------------------------------------------------------+

1 row in set (0.00 sec)

mysql> SELECT * FROM test;

+------+------+

| id | NAME |

+------+------+

| 1 | a1 |

| 2 | a2 |

| 3 | a3 |

| 4 | a4 |

+------+------+

4 rows in set (0.00 sec)