sql 存储过程参数为空则不作为条件

/****** Object:  StoredProcedure [dbo].[GetCommonGroupByRegion]    Script Date: 03/23/2017 17:31:18 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO


ALTER proc  [dbo].[GetCommonGroupByRegion]
@CarCategory  varchar(50)=null,---车型
@CreateTimeStart datetime=null,  --入会开始时间
@CreateTimeEnd datetime=null,    --入会结束时间
@AuthenticationTimeStart datetime=null,    --认证开始时间
@AuthenticationTimeEnd datetime=null,    --认证结束时间
@BuyTimeStart datetime=null,    --购车开始时间
@BuyTimeEnd datetime=null    --购车结束时间

as
begin


DECLARE @strPC VARCHAR(2000), @strAPP VARCHAR(2000), @strWX VARCHAR(2000), @strWAP VARCHAR(2000)
---------------------pc start
SET @strPC = ( SELECT DISTINCT STUFF(
    ( SELECT ','''+ qudao+'''' FROM CreatedType WITH ( NOLOCK )
      WHERE   qtype = 'pc' ORDER BY qudao
      FOR XML PATH('')), 1,4, '') AS jzhw
    FROM   CreatedType t) 
set @strPC= left(@strPC,len(@strPC)-1)
-------------------------pc end***********
------------------------app start
SET @strAPP = ( SELECT DISTINCT STUFF(
    ( SELECT ','''+ qudao+'''' FROM CreatedType WITH ( NOLOCK )
      WHERE   qtype = 'app' ORDER BY qudao
      FOR XML PATH('')), 1,4, '') AS jzhw
    FROM   CreatedType t) 
set @strAPP= left(@strAPP,len(@strAPP)-1)
------------------------- app end *******
------------------------wx start
SET @strWX = ( SELECT DISTINCT STUFF(
    ( SELECT ','''+ qudao+'''' FROM CreatedType WITH ( NOLOCK )
      WHERE   qtype = 'wx' ORDER BY qudao
      FOR XML PATH('')), 1,4, '') AS jzhw
    FROM   CreatedType t) 
set @strWX= left(@strWX,len(@strWX)-1)
------------------------- wx end *******
------------------------wap start
SET @strWAP = ( SELECT DISTINCT STUFF(
    ( SELECT ','''+ qudao+'''' FROM CreatedType WITH ( NOLOCK )
      WHERE   qtype = 'wap' ORDER BY qudao
      FOR XML PATH('')), 1,4, '') AS jzhw
    FROM   CreatedType t) 
set @strWAP= left(@strWAP,len(@strWAP)-1)
------------------------- wap end *******
 select  
 c.CarCategory as '车型',
 d.Region as '区域',
 COUNT(case when a.CreatedPerson like '%D%' and  len(a.CreatedPerson)=5 then a.Id else null end ) as '经销商',
 COUNT(case when a.CreatedPerson in( @strPC)  then a.Id else null end ) as '网站',

 COUNT(case when a.CreatedPerson in(@strAPP) then a.Id else null end ) as 'APP',

 COUNT(case when a.CreatedPerson in(@strWX) then a.Id else null end ) as '微信',
 
 COUNT(case when a.CreatedPerson in( @strWAP) then a.Id else null end ) as 'wap'
  from   
   Membership  a
 left join IF_Customer b  on a.IdentityNumber=b.IdentityNumber
 left join IF_Car  c on b.CustId=c.CustId
 left join CS_CarDealerShip  d on c.DealerId=d.DealerId
 where 
 a.IsDel=0  
 
 --case when @CreateTimeStart is not null then  and a.CreateTime>@CreateTimeStart else null end 
 --and ( (@CreateTimeStart is not null and @CreateTimeStart!='') and (a.CreateTime>@CreateTimeStart) )
 --and ( (@CreateTimeEnd is not null and @CreateTimeEnd!='') and (a.CreateTime<=@CreateTimeEnd) )
 
 and (a.CreateTime>=@CreateTimeStart or @CreateTimeStart is null) 
 and (a.CreateTime<=@CreateTimeEnd or @CreateTimeEnd is null) 
 
 --and ( (@AuthenticationTimeStart is not null and @AuthenticationTimeStart!='') and (a.AuthenticationTime>@AuthenticationTimeStart) )
 --and ( (@AuthenticationTimeEnd is not null and @AuthenticationTimeEnd!='') and (a.AuthenticationTime<=@AuthenticationTimeEnd) )
  
 and (a.AuthenticationTime>=@AuthenticationTimeStart or @AuthenticationTimeStart is null) 
 and (a.AuthenticationTime<=@AuthenticationTimeEnd or @AuthenticationTimeEnd is null) 
 
 
 --and ( (@CarCategory is not null and @CarCategory!='') and (c.CarCategory=@CarCategory) )
 and (c.CarCategory=@CarCategory or @CarCategory is null ) 
 
 --and ( (@BuyTimeStart is not null and @BuyTimeStart!='') and ( c.BuyTime>@BuyTimeStart) )
 --and ( (@BuyTimeEnd is not null and @BuyTimeEnd!='') and ( c.BuyTime<=@BuyTimeEnd) )
 
 and (c.BuyTime>=@BuyTimeStart or @BuyTimeStart is null) 
 and (c.BuyTime<=@BuyTimeEnd or @BuyTimeEnd is null) 
 
 
 and d.Region<>''
 and d.Region<>'-'
 group by  c.CarCategory, d.Region 
 ;
 
 end
 

解析：   and (c.BuyTime<=@BuyTimeEnd or @BuyTimeEnd is null) 

首先 and 条件后面是括号，那就说明括号 是一个整体，  括号里面 用的 or 语法，也就说明只要任意一个条件满足就ok, 当参数为空的时候，假如作为条件的字段是时间格式的，如果做大小比较肯定会失败，这个时候后面的 or的条件满足了，就把前面的给忽略了，其实这个时候就相当于  and 1=1 了，