在实际开发中，尤其是在做权限管理的时候，常常要对对某个用户的权限进行检索，本文给出SQL Server中的一个实例.

--用户继承树
CREATE function getUserTree(@UserName sysname,  --用户名
                           @Seq bit     --查找方式:0查找子孙  1.查找祖先
                           )
  returns @Result table(UserID sysname,UserName sysname,Level int)
as
begin
    declare @UserId sysname
    set @userId=user_id(@userName)   
   
    if @userid is null
    begin
      --raiserror('指定的用户名不存在',16,1)
      return
    end
   
 DECLARE @level int, @line char(20)
 declare @stack table(item sysname, level int)
 INSERT INTO @stack VALUES (@UserID, 1)
 SELECT @level = 1
 
 WHILE @level > 0
 BEGIN
    IF EXISTS (SELECT * FROM @stack WHERE level = @level)
       BEGIN
          SELECT @userId = item
          FROM @stack
          WHERE level = @level
             insert into @Result values(@UserId,User_name(@userID),@level)

          DELETE FROM @stack
          WHERE level = @level
             AND item = @userId
            
             if @Seq=1  --查找祖先
              INSERT @stack
                SELECT groupuid, @level + 1
                FROM sysmembers
                WHERE memberuid = @userId
             else  --查找子孙
              INSERT @stack
                SELECT memberuid, @level + 1
                FROM sysmembers
                WHERE groupuid = @userId

          IF @@ROWCOUNT > 0
             SELECT @level = @level + 1
       END
    ELSE
       SELECT @level = @level - 1
 END -- WHILE    
   
  return
end

实例：
exec sp_addrole 'Users'
exec sp_addrole 'BusinessMan'
exec sp_addrolemember 'Users','BusinessMan'
exec sp_addrole 'Saler'
exec sp_addrolemember 'BusinessMan','Saler'

exec sp_addlogin 'OrderMan','OrderMan','lifeng'
exec sp_addrolemember 'Saler','OrderMan'
exec sp_grantdbaccess 'OrderMan','OrderMan'
select * from getUserTree('OrderMan',1)

结果显示
UserID   USRENAME     Level
5              OrderMan          1
16402     Saler                  2
16401     BusinessMan  3
16403     Users                4

这种方法，也在MRP/ERP系统中遍历BOM时使用