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有没有办法在 IN() 语句中嵌套 CASE-WHEN 语句，以便 WHEN 或 ELSE 之一返回子查询。对我来说，这不应该是一个问题，但不知何故我得到了错误：

“子查询返回超过 1 个值。”

IN()应该处理多个值！

这是一个重现错误的小示例：

-- tblA will be searched for values
Declare @tblA  table (i int)
insert @tblA
    select 1
    union select 2
    union select 3

--tblB: its values will be searched in tblA
Declare @tblB  table (i int)
insert @tblB
    select 2
    union select 3
    union select 1

--@c used by the CASE statement to match
declare @c varchar(50)
set @c = 'Match'

select *
from @tblA
where i IN ( -- IN statement should accept subquery in it
    case @c
        when 'Dont Match' then 2 --If it had matched, then the single value 2 would have been returned and TSQL would be happy
        else (
            select i from @tblB --TSQL not happy and causing error when more than one values returned from the subquery
        )
    end
)
4

3 回答 3

2

尝试

select *
from @tblA A
WHERE (@c = 'Dont Match' AND i = 2) OR 
(@c <> 'Dont Match' AND EXISTS (SELECT * FROM @tblB WHERE i = A.i)
于 2013-09-19T08:04:41.153 回答
1

您的问题不在于 IN 子句，而在于 CASE。
CASE 不能处理多个值。
有效的 

DECLARE @TBLA  TABLE (I INT)
INSERT INTO @TBLA
        ( [I] )
SELECT 0

SELECT [Result]=CASE WHEN 1=2 THEN 
    (SELECT I FROM @TBLA T) 
ELSE 
    (SELECT I FROM @TBLA T) 
END


无效，因为表变量包含两条记录。 

DECLARE @TBLA  TABLE (I INT)
INSERT INTO @TBLA
        ( [I] )
SELECT 0
UNION 
SELECT 1


SELECT [Result]=CASE WHEN 1=2 THEN 
    (SELECT I FROM @TBLA T) 
ELSE 
    (SELECT I FROM @TBLA T) 
END
于 2013-09-19T06:03:05.467 回答
0 
IN() is supposed to handle more than one values!

是的，确实如此。如果您以这种方式修改查询，您可以看到它

select *
from @tblA
where i IN ( select i from @tblB )

此查询将被正确执行。该错误是由语句产生的，因为它在or子句CASE中不能获得超过 1 个值。THENELSE

于 2013-09-19T04:54:49.133 回答