MySQL中replace的使用

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MySQL中replace的使用

1.使用原则

如果原表中有该条数据，那么会将该条数据删除；如果原表中没有该条数据，则会插入指定值

REPLACE INTO [table_name](fields) VALUES(value...);

2.实战案例

mysql> select * from cities;
+----+-------------+------------+
| id | name        | population |
+----+-------------+------------+
|  1 | New York    |    8008278 |
|  2 | Los Angeles |    3694825 |
|  3 | Shanghai    |    1923400 |
+----+-------------+------------+
3 rows in set (0.00 sec)

mysql> UPDATE cities SET
    -> population = 1008256
    -> WHEREid = 1;
Query OK, 1 row affected (0.08 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> REPLACE INTO cities(id,population) VALUES(2,3696820);
Query OK, 2 rows affected (0.06 sec)

mysql> SELECT  * FROM  cities;
+----+----------+------------+
| id | name     | population |
+----+----------+------------+
|  1 | New York |    1008256 |
|  2 | NULL     |    3696820 |
|  3 | Shanghai |    1923400 |
+----+----------+------------+
3 rows in set (0.00 sec)