MySQL 为什么我的“INSERT ... ON DUPLICATE KEY UPDATE”中有两行受到影响？
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Why are 2 rows affected in my `INSERT ... ON DUPLICATE KEY UPDATE`?
提问by Josh Smith
I'm doing an INSERT ... ON DUPLICATE KEY UPDATEfor a PRIMARY KEYin the following table:
我正在INSERT ... ON DUPLICATE KEY UPDATE为PRIMARY KEY下表中的a做一个：
DESCRIBE users_interests;
+------------+---------------------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+---------------------------------+------+-----+---------+-------+
| uid | int(11) | NO | PRI | NULL | |
| iid | int(11) | NO | PRI | NULL | |
| preference | enum('like','dislike','ignore') | YES | | NULL | |
+------------+---------------------------------+------+-----+---------+-------+
However, even though these values should be unique, I'm seeing 2 rows affected.
但是，即使这些值应该是唯一的，我也看到有 2 行受到影响。
INSERT INTO users_interests (uid, iid, preference) VALUES (2, 2, 'like')
ON DUPLICATE KEY UPDATE preference='like';
Query OK, 2 rows affected (0.04 sec)
Why is this happening?
为什么会这样？
EDIT
编辑
For comparison, see this query:
要进行比较，请参阅此查询：
UPDATE users_interests SET preference='like' WHERE uid=2 AND iid=2;
Query OK, 1 row affected (0.44 sec)
Rows matched: 1 Changed: 1 Warnings: 0
回答by ChristopheD
From the manual:
从手册：
With ON DUPLICATE KEY UPDATE, the affected-rows value per row is 1 if the row is inserted as a new row and 2 if an existing row is updated.
使用 ON DUPLICATE KEY UPDATE，如果将行作为新行插入，则每行的受影响行值为 1，如果更新现有行，则为 2。
回答by ontrack
So you know whether you updated a row (duplicate key) or just inserted one: http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html
所以你知道你是更新了一行（重复键）还是只是插入了一个：http: //dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html
