Question

我想在查询中分配一些变量，这些变量对其列使用CASE语句。不太确定如何做到这一点，无法找到正确的语法。

这是我到目前为止所做的，但它有语法错误。

 -- set @theID and @theName with their appropriate values
 select top (1) 
 @theID = (Case when B.ID IS NULL then A.ID else B.ID END) ,
 @theName = (Case when B.Name IS NULL then A.Name else B.Name END) 
 from B left join A on A.ID = B.ID where ...

将这些变量粘贴在那里的正确位置/方法是什么？

Answer 1

你给出的例子应该有效。您可以从案例陈述中分配变量。只是假装整个CASE..WHEN..THEN..ELSE..END块是一个字段。这是一个通用的例子：

declare
  @string1 nvarchar(100) = null
 ,@string2 nvarchar(100) = null
 ;

select top 1
  @string1 = case when 1=1 then 'yes' else 'no' end
 ,@string2 = case when 1=0 then 'yes' else 'no' end

print 'string1 = ' + @string1
print 'string2 = ' + @string2

给出：

string1 = yes
string2 = no

您能告诉我们您遇到的具体错误吗？

Answer 2

您可以使用ISNULL或COALESCE：

更轻松地完成此操作

select top (1) 
 @theID = ISNULL(B.ID, A.ID),
 @theName = ISNULL(B.Name, A.Name),
 from B left join A on A.ID = B.ID where ...

Answer 3

DECLARE @SmallBlindSeatId INT  
DECLARE @BigBlindSeatId INT  
DECLARE @DealerSeatId INT  
DECLARE @NextTurn INT  

SELECT @DealerSeatId=( CASE WHEN BlindsInfo=1 THEN SeatId ELSE @DealerSeatId END ),
@SmallBlindSeatId=( CASE WHEN BlindsInfo=2 THEN SeatId ELSE @SmallBlindSeatId END),
@BigBlindSeatId=( CASE WHEN BlindsInfo=3 THEN SeatId ELSE @BigBlindSeatId END),
@NextTurn=( CASE WHEN NEXTTURN=1 THEN SeatId ELSE @NextTurn END)

FROM ABC WHERE TESTCASEID=1

PRINT(@DealerSeatId)

PRINT(@SmallBlindSeatId)

PRINT(@BigBlindSeatId)

PRINT (@NextTurn)

从CASE语句分配给T-SQL变量

3 个答案: