INSERT ON DUPLICATE KEY UPDATE

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语法

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
  [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
  {VALUES | VALUE} ({expr | DEFAULT},...),(...),...
  [ ON DUPLICATE KEY UPDATE
    col=expr
      [, col=expr] ... ]

或:

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)]
    SET col={expr | DEFAULT}, ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ]

或:

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
    SELECT ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ]

描述

INSERT ... ON DUPLICATE KEY UPDATE是MariaDB/MySQL对INSERT语句的扩展,当插入数据的时候发现有重复值冲突,将对原记录执行UPDATE操作来替代INSERT操作。

当插入数据的时候没有执行UPDATE而是单纯地插入数据,受影响的行数为1,如果执行了UPDATE操作,受影响的行数为2,除非设置了API的CLIENT_FOUND_ROWS标记。

如果有多个unique索引被匹配,则只有第一个会被更新。因此,对于有多个唯一索引的表,不建议使用该语句来插入数据。

如果表具有AUTO_INCREMENT的主键列,且插入了或更新了一行,则LAST_INSERT_ID()函数将返回它的AUTO_INCREMEN值。

VALUES()函数只能应用在ON DUPLICATE KEY UPDATE子句中,在其他格式的INSERT语句中该函数无意义。它会返回INSERT语句中列对应的值。该函数在多行插入的环境中非常有用。

如果使用了 ON DUPLICATE KEY UPDATE子句,则IGNOREDELAYED选项会被忽略。

MariaDB starting with 10.0

PARTITION子句是从MariaDB 10.0开始引入的,详细信息见Partition Pruning and Selection

该语句会激活INSERT和UPDATE触发器。详细信息见Trigger Overview

还有一个与之类似的语句REPLACE

示例

CREATE TABLE ins_duplicate (id INT PRIMARY KEY, animal VARCHAR(30));
INSERT INTO ins_duplicate VALUES (1,'Aardvark'), (2,'Cheetah'), (3,'Zebra');

由于没有键值重复冲突,下面的语句将以普通的INSERT操作插入数据:

INSERT INTO ins_duplicate VALUES (4,'Gorilla') ON DUPLICATE KEY UPDATE animal='Gorilla';
Query OK, 1 row affected (0.07 sec)
SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Aardvark |
|  2 | Cheetah  |
|  3 | Zebra    |
|  4 | Gorilla  |
+----+----------+

由于键值重复,下面的INSERT语句插入失败:

INSERT INTO ins_duplicate VALUES (1,'Antelope');
ERROR 1062 (23000): Duplicate entry '1' for key 'PRIMARY'

此时,可以使用INSERT ON DUPLICATE KEY UPDATE来更新重复值:

INSERT INTO ins_duplicate VALUES (1,'Antelope') ON DUPLICATE KEY UPDATE animal='Antelope';
Query OK, 2 rows affected (0.09 sec)

注意,上面的语句将会报告受影响的行数为2,这是UPDATE的行为。

SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Antelope |
|  2 | Cheetah  |
|  3 | Zebra    |
|  4 | Gorilla  |
+----+----------+

添加一个新的具有唯一性的字段:

ALTER TABLE ins_duplicate ADD id2 INT;
UPDATE ins_duplicate SET id2=id+10;
ALTER TABLE ins_duplicate ADD UNIQUE KEY(id2);

由于匹配了两个唯一键,因此只有第一个被匹配的键被更新。这是不安全的行为,因此不推荐在多个唯一键的表上执行INSERT ON DUPLICATE KEY UPDATE语句,除非你直到自己在做什么。注意,下面的警告只在MariaDB 5.5之前才会显示,在MariaDB 10.0中已经移除了,因为MariaDB假定按照顺序去检查各个键,顺序可由SHOW CREATE TABLE获取。

INSERT INTO ins_duplicate VALUES (2,'Lion',13) ON DUPLICATE KEY UPDATE animal='Lion';
Query OK, 2 rows affected, 1 warning (0.06 sec)

SHOW WARNINGS;
+-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level | Code | Message                                                                                                                                                                                  |
+-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Note  | 1592 | Unsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT. INSERT... ON DUPLICATE KEY UPDATE  on a table with more than one UNIQUE KEY is unsafe |
+-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

SELECT * FROM ins_duplicate;
+----+----------+------+
| id | animal   | id2  |
+----+----------+------+
|  1 | Antelope |   11 |
|  2 | Lion     |   12 |
|  3 | Zebra    |   13 |
|  4 | Gorilla  |   14 |
+----+----------+------+

尽管第三行id=3对应的id2=13也被INSERT语句匹配到了,但却没有去更新该行的记录。

将id字段更改为自增字段auto_increment。如果insert插入了一个新行,auto_increment的只将向前移动。如果更新了已存在的行,则auto_increment保留原有的值。

ALTER TABLE `ins_duplicate` CHANGE `id` `id` INT( 11 ) NOT NULL AUTO_INCREMENT;
ALTER TABLE ins_duplicate DROP id2;
SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              5 |
+----------------+

INSERT INTO ins_duplicate VALUES (2,'Leopard') ON DUPLICATE KEY UPDATE animal='Leopard';
Query OK, 2 rows affected (0.00 sec)

SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              5 |
+----------------+

INSERT INTO ins_duplicate VALUES (5,'Wild Dog') ON DUPLICATE KEY UPDATE animal='Wild Dog';
Query OK, 1 row affected (0.09 sec)

SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Antelope |
|  2 | Leopard  |
|  3 | Zebra    |
|  4 | Gorilla  |
|  5 | Wild Dog |
+----+----------+

SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              6 |
+----------------+

从INSERT语句中引用字段的值来更新数据:

INSERT INTO table (a,b,c) VALUES (1,2,3),(4,5,6)
    ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b);

更多内容参见VALUES()函数。

See Also

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