Question

我有一个mysql表如下：

name | serialno | key
---------------------
NULL | NULL     | 10
luke | 1234     | 20
NULL | NULL     | 30
NULL | NULL     | 40

我必须更新有效密钥name和serialno更新的行。

我正在运行的更新语句如下：

UPDATE test SET Name = 'pc', Serialno = '10', WHERE `Key` = '10' AND name is null

和

UPDATE test SET Name = CASE
WHEN NULL THEN 'pc'
END
SET Serialno = CASE
WHEN NULL THEN '10'
END
Where `key` = '20'

显示以下错误：

1

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE Key = '10' AND name is null' at line 1:

2

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SET Serial = CASE
WHEN NULL THEN '10'
END
Where `key`='20'' at line 4:

请帮忙。

Answer 1

UPDATE test SET Name = CASE Name
WHEN NULL THEN 'pc'
END,
SET Serialno = CASE Serialno 
WHEN NULL THEN '10'
END
Where `key` = '20'

您必须指定CASE的条件

Answer 2

我不知道上下文是什么（你能解释你想要的细节，然后我会帮助你获得更好的结果）。

然而，正如StanislavL的回答，语法错误。我更正了如下：

UPDATE test SET Name = CASE Name
WHEN NULL THEN 'pc'
END,
Serialno = CASE Serialno 
WHEN NULL THEN '10'
END
Where `key` = '20'

Answer 3

错误的原因：

错误1 是因为您在,之前有一个WHERE Key = '10' ... 逗号。
声明应该是：

UPDATE test SET Name = 'pc', Serialno = '10' WHERE `Key` = '10' AND name is null

错误2 是因为您没有指示要检查哪个案例值 when子句。可接受的语法是：

1. CASE column_name WHEN value THEN expr1 ELSE expr2 END  

2. CASE WHEN column_name <condition> value THEN expr1 ELSE expr2 END

声明应该是：

UPDATE test 
SET
    Name     = CASE WHEN name IS NULL THEN 'pc' else name end
  , Serialno = CASE WHEN serialno IS NULL THEN '10' else serialno end
END
Where `key` = '10'

示例 @ SQL Fiddle

您可以对此进行扩展，以根据不同的key值设置列的值，而不使用where子句。

示例：

UPDATE test 
SET
    Name     = CASE WHEN `key`=10 and name IS NULL THEN 'pc' else name end
  , Serialno = CASE WHEN `key`=10 and serialno IS NULL THEN '10' else serialno end

  , Name     = CASE WHEN `key`=30 and name IS NULL THEN 'key is 30' else name end
  , Serialno = CASE WHEN `key`=30 and serialno IS NULL THEN '3' else serialno end
END

请参阅：MySQL: CASE - WHEN syntax

Answer 4

请这样做

UPDATE test SET Name = 'pc', Serialno = '10' WHERE `Key` = '10' AND name is null

mysql-使用多个where子句更新单行中的多个列

4 个答案: