一个Case When条件语句求解解决思路

一个Case When条件语句求解
表A,表B

SQL code

Select * From 表A Where .....

SQL code

Select ItemName From 表B Where plan_id=@plan_id 

SQL code

Select * From 表A 

SQL code

Select * From 表A Where ID IN (Select ItemName From 表B Where plan_id=@plan_id )

SQL code

Select ItemName From 表B Where plan_id=@plan_idif (@@rowcount = 1) and (ItemName   =   'xx')    Select * From 表Aelse    Select * From 表A Where ID IN (Select ItemName From 表B Where plan_id=@plan_id )
[解决办法]
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''')
[解决办法]
使用
if else
SQL code
declare @ID intset @ID = 1if @ID = 1beginselect COunt(*) from  sysobjectsset @ID = 2endelseselect count(*) from sysfiles
[解决办法]
if @@rowcount = 1 and Case_ItemID = 'All'
????????????????////////
郁闷，怎么能这样用的
----------------
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 =@Plan_ID  and Case_name = 'account'if @@rowcount = 1 and @Case_ItemID = 'All'   select @DisplayChar = ''else   select @DisplayChar = '1'