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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)