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)
)
