Sql Server中如何通過父記錄查找出所有關聯的子記錄

可查4級Sql代碼

select menu_id,menu_name,Father_Id from Sys_Menu where menu_id='18' or Father_Id=18 or -- 一級、二級  
Father_Id in (select menu_id from Sys_Menu a where  menu_id='18' or Father_Id=18) or   -- 三級  
father_id in (select menu_id from sys_menu where Father_Id in (select menu_id from Sys_Menu a where  menu_id='18' or Father_Id=18)) -- 四級

select menu_id,menu_name,Father_Id from Sys_Menu where menu_id='18' or Father_Id=18 or -- 一級、二級

Father_Id in (select menu_id from Sys_Menu a where  menu_id='18' or Father_Id=18) or   -- 三級

father_id in (select menu_id from sys_menu where Father_Id in (select menu_id from Sys_Menu a where  menu_id='18' or Father_Id=18)) -- 四級