一个Case When条件语句求解解决思路

Select * From 表A Where .....

Select ItemName From 表B Where [email protected]_id 

Select * From 表A 

Select * From 表A Where ID IN (Select ItemName From 表B Where [email protected]_id )

Select ItemName From 表B Where [email protected]_idif (@@rowcount = 1) and (ItemName   =   'xx')    Select * From 表Aelse    Select * From 表A Where ID IN (Select ItemName From 表B Where [email protected]_id )
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SQL code
drop table tbcreate table tb (id int,AN varchar(8000),CN varchar(8000))insert tb select 1,'a','121'insert tb select 2,'','123'insert tb select 3,'s','123'create table tb (id int,AN varchar(8000),CN varchar(8000))insert tb select 1,'a','121'insert tb select 2,'','123'if(exists(select 1 from tb where an != '' and cn='123') ) exec('select * from tb where an !='''' and cn =''123''')elseexec('select * from tb where an ='''' and cn =''123''')
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使用
if else
SQL code
declare @ID intset @ID = 1if @ID = 1beginselect COunt(*) from  sysobjectsset @ID = 2endelseselect count(*) from sysfiles
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if @@rowcount = 1 and Case_ItemID = 'All'
????????????????////////
郁闷，怎么能这样用的
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SQL code
declare @DisplayChar intdeclare @Plan_ID intdeclare @Case_ItemID varchar(20)set @Plan_ID  ='1006'Select @Case_ItemID = Ltrim(Case_ItemID) From Report_Planparameter2       Where Plan_Id [email protected]_ID  and Case_name = 'account'if @@rowcount = 1 and @Case_ItemID = 'All'   select @DisplayChar = ''else   select @DisplayChar = '1'