MySQL 中多个案例的语法

Question

我有一个 MySQL 更新语句试图重置两列：label 和 PersTrCode。（这是在 Coldfusion 程序中。）我正在使用 CASE 语句执行此操作，但我似乎无法获得正确的语法——我不断收到错误消息。代码：

<cfquery name = 'nonull' datasource = "Moxart">
update FinAggDb
set Label = CASE 
 WHEN PersActIncOutg = 'I' && PersTrCode IS NULL THEN 'Total Income'
 WHEN PersActIncOutg = 'O' && PersTrCode IS NULL THEN 'Total Expense'
 WHEN PersActIncOutg IS NULL && PersTrCode IS NULL THEN ' '
 ELSE PersTrCode
END 
SET PersTrCode = CASE 
 WHEN PersTrCode IS NULL THEN 'Total'
 ELSE PersTrCode
END 
</cfquery>

错误是通常的提示性语句：

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 PersTrCode = CASE WHEN PersTrCode IS NULL THEN 'Total' ELSE PersTrCode ' at line 8

是否不允许多个CASE语句？或者谁能告诉我如何解决这个问题？

Answer 1

一条更新语句只有一个set子句，要更新的各个列之间用逗号隔开。另外，请注意，使用 and 而不是 && 更常见，尽管两者在 MySQL:

中都有效

update FinAggDb
set Label = CASE 
 WHEN PersActIncOutg = 'I' AND PersTrCode IS NULL THEN 'Total Income'
 WHEN PersActIncOutg = 'O' AND PersTrCode IS NULL THEN 'Total Expense'
 WHEN PersActIncOutg IS NULL AND PersTrCode IS NULL THEN ' '
 ELSE PersTrCode
END
,  -- comma here, not a second "set" clause
PersTrCode = CASE 
 WHEN PersTrCode IS NULL THEN 'Total'
 ELSE PersTrCode
END

MySQL 中多个案例的语法

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