Assign to a T-SQL variable from a CASE statement

I'd like to assign some variables inside a query that uses CASE statements for it's columns. Not quite sure how to do this, having trouble finding the right syntax.

This is what I have so far, but it's got syntax errors.

 -- set @theID and @theName with their appropriate values
 select top (1) 
 @theID = (Case when B开发者_开发知识库.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 ...

What's the correct place/way to stick those variables in there?

The example you've given should work. You can assign to variables from a case statement. Just pretend that the entire CASE..WHEN..THEN..ELSE..END block is a field. Here is a generic example:

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

select
  @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

Gives:

string1 = yes
string2 = no

Can you tell us what specific error(s) you are getting?

You could probably do this more easily using ISNULL or COALESCE:

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 ...

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)