SQL_之 递归_START WITH id ='102' CONNECT BY PRIOR pid=id

oracle 递归用法

SELECT *
FROM menu
START WITH id ='102'
CONNECT BY PRIOR pid=id

　一种应用　

SELECT *
  FROM menu a
 START WITH id in (select menu_id from role_menu where role_code = '005')
CONNECT BY PRIOR id = pid)

　　解释:不太明白为什么,

这个时候查出来的数据是重复的

SELECT a.id
  FROM menu a
 START WITH id in (select id from menu)
CONNECT BY PRIOR id = pid

　　

查出来的数据还是重复的.

        select *
          from menu
         where id in
               (SELECT a.id
                  FROM menu a
                 START WITH id in
                            (select menu_id from role_menu where role_code = '005')
                CONNECT BY PRIOR id = pid)