MySQL 5.5 INSERT ON DUPLICATE KEY UPDATE語句解說

2024-07-24 12:32:46

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執行INSERT ... ON DUPLICATE KEY UPDATE語句，如果INSERT的語句插入的值和已有的UNIQUE索引或主鍵重復的話，MySQL會更新已存在的行。
測試沒有主鍵和UNIQUE索引的表

mysql> select * from dept2;
+--------+-------------+-------------+
| deptno | dname       | report_date |
+--------+-------------+-------------+
|     10 | Research    | 2016-06-03 |
|     20 | Maintenance | 2016-06-03 |
|     30 | Leader      | 2016-06-03 |
|     40 | Market      | 2015-08-02 |
+--------+-------------+-------------+
4 rows in set (0.00 sec)

mysql> desc dept2;
+-------------+-------------+------+-----+---------+-------+
| Field       | Type        | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+-------+
| deptno      | int(5)      | NO   | MUL | NULL    |       |
| dname       | varchar(14) | YES |     | NULL    |       |
| report_date | date        | YES | MUL | NULL    |       |
+-------------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql> INSERT INTO dept2 (deptno,dname,report_date) VALUES (20,'Development','2010-10-30')
->   ON DUPLICATE KEY UPDATE report_date='2010-10-30';
Query OK, 1 row affected (0.01 sec)

mysql> select * from dept2;
+--------+-------------+-------------+
| deptno | dname       | report_date |
+--------+-------------+-------------+
|     10 | Research    | 2016-06-03 |
|     20 | Maintenance | 2010-10-30 |
|     30 | Leader      | 2016-06-03 |
|     40 | Market      | 2015-08-02 |
+--------+-------------+-------------+
4 rows in set (0.00 sec)

（編輯：武林網）

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