sql 多级内查询

最近在开发一个外包的项目，其中有个需求，一直困扰我好几天，今天终于找到了解决方案。大致需求如下：公司总部发货给经销商，其中经销商包含四种级别，钻石、金牌、银牌和铜牌，等级依次下发，钻石包含金牌，金牌包含银牌，银牌包含铜牌，铜牌下面有终端客户，也就是产品的终端，给客户使用。

如果系统登陆的是钻石经销商，需要查询他的客户，需要把最底层的经销商查出来，最后，查询所属的终端客户。

大致的存储过程：

USE [DbDevice]
GO
/****** Object:  StoredProcedure [dbo].[Pro_FindMaterialByTerminalId]    Script Date: 07/14/2014 14:21:39 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:  <Author,,Name>
-- Create date: <Create Date,,>
-- Description: <Description,,>
-- =============================================
ALTER PROCEDURE [dbo].[Pro_FindMaterialByTerminalId]
@DealerId varchar(50),
@MaterialName varchar(50),
@StartDate varchar(50),
@EndDate varchar(50)
AS
BEGIN
 SET NOCOUNT ON;
 declare @where varchar(1000)
 declare @sql varchar(1000)
 declare @select varchar(800)
 declare @order varchar(100)
 declare @type int
 set @where=' '
 set @sql=''
 set @select=''
 set @order=''
 set @type=(select t.Level from Tbl_Dealer t where t.DealerId=@DealerId)
 
 if(@MaterialName<>'') set @where=@where+' And A1.SerialNumber='+@MaterialName
 set @where=@where+' And A1.UseTime>='''+@StartDate+''' And A1.UseTime<='''+@EndDate+''''
 
 if(@type=0)
 begin
      set @select=' select A1.TypeId,A1.SerialNumber,A1.CreateTime,B1.TerminalName,A1.Barcode,A1.ProvinceId,A1.DeviceId,A1.UseTime, A1.Status  from Tbl_Material A1 ,Tbl_Terminal B1
      
      where A1.TerminalId=B1.TerminalId And A1.TerminalId in (select A.TerminalID
    from Tbl_Terminal A
    where A.DealerId in (select H.DealerId From Tbl_Dealer H where H.ParentId in(
   select G.DealerId From Tbl_Dealer G where G.ParentId in(
   select F.DealerId From Tbl_Dealer F where F.ParentId in
   (select E.DealerId from Tbl_Dealer E where E.DealerId='''+@DealerId+''')))))'
 end
 if(@type=1)
 begin
    set @select=' select A.TerminalID
    from Tbl_Terminal A
    where A.DealerId in (
   select G.DealerId From Tbl_Dealer G where G.ParentId in(
   select F.DealerId From Tbl_Dealer F where F.ParentId in
   (select E.DealerId from Tbl_Dealer E where E.DealerId='''+@DealerId+''')))'
 end
 if(@type=2)
 begin
   set @select=' select A.TerminalID
    from Tbl_Terminal A
    where A.DealerId in (
   select F.DealerId From Tbl_Dealer F where F.ParentId in
   (select E.DealerId from Tbl_Dealer E where E.DealerId='''+@DealerId+'''))'
 end
 if(@type=3)
 begin
   set @select=' select A.TerminalID
    from Tbl_Terminal A
    where A.DealerId in (
   select E.DealerId from Tbl_Dealer E where E.DealerId='''+@DealerId+''')'
 end
 
 set @order=' order by A1.UseTime desc'
 set @sql=@select+@where+@order
 print @sql
 exec (@sql)
END