SQL：CASE WHEN用或者在

Question

假設存儲過程得到3個參數;這些都是boolean（1或0）： @includeMode1，@includeMode2，@includeMode3

我想這樣做的查詢：

SELECT * 
FROM [dbo].[MyTable] as P 
WHERE P.Mode = 1 (if @includeMode1 = 1) OR P.Mode = 2 (if @includeMode2 = 1) OR P.Mode = 3 (if @includeMode3 = 1) 

我似乎無法找到正確的方法，也很高興聽到是否有更有效的方法（性能）來取代or

Answer 1

如果所有三可「1」，那麼這樣的：

SELECT * 
FROM [dbo].[MyTable] as P 
WHERE (P.Mode = 1 and @includeMode1 = 1) 
    OR (P.Mode = 2 and @includeMode2 = 1) 
    OR (P.Mode = 3 and @includeMode3 = 1) 

Answer 2

SELECT * FROM [dbo].[MyTable] as P 
WHERE P.Mode = CASE WHEN @includeMode1 = 1 THEN 1 ELSE 0 END OR 
    P.Mode = CASE WHEN @includeMode2 = 2 THEN 2 ELSE 0 END OR 
    P.Mode = CASE WHEN @includeMode3 = 3 THEN 3 ELSE 0 END 

Answer 3

一種有效的方式來代替or s就使用dynamic sql。

rextester：http://rextester.com/RFHEC49942

create procedure [mytable_get_byMode] (@IncludeMode1 bit, @IncludeMode2 bit, @IncludeMode3 bit) as 
begin; 
    if coalesce(nullif(@IncludeMode1,0),nullif(@IncludeMode2,0),nullif(@IncludeMode3,0))=convert(bit,1) 
    begin; 
    declare @sql nvarchar(4000) 
    select @sql =N'select * 
    from [dbo].[MyTable] as P 
    where P.Mode in (' 
    +stuff(case when @IncludeMode1 = 1 then ',1' else '' end 
     +case when @IncludeMode2 = 1 then ',2' else '' end 
     +case when @IncludeMode3 = 1 then ',3' else '' end 
     ,1,1,'') 
     +N');'; 
    select @sql; 
    --exec sp_executesql @sql; 
    end; 
end; 
go 
exec mytable_get_byMode 1,1,1; 
exec mytable_get_byMode 0,1,1; 
exec mytable_get_byMode 1,0,1; 
exec mytable_get_byMode 0,0,0;