Oracle 转 postgresql 递归 connect_by_isleaf 方案

oracle:

SELECT
        user_number,
        LTRIM( SYS_CONNECT_BY_PATH ( NAME, ‘,‘ ), ‘,‘ ) NAME
        ,RN
    FROM
        (
        SELECT
            u.user_number,
            r.NAME,
            ROW_NUMBER ( ) OVER ( PARTITION BY u.user_number ORDER BY ur.role_id ) RN
        FROM
            ems_role r,
            ( SELECT ur.user_id, ur.role_id FROM ems_user_role ur
            UNION SELECT ur.user_id, ur.role_id FROM ems_user_device_role ur ) ur,
            ems_user u
        WHERE
            ur.user_id = u.ID
            AND r.ID = ur.role_id
        )
    WHERE
        1=1
            and connect_by_isleaf = 1
        START WITH rn = 1 CONNECT BY RN - 1 = PRIOR RN
        AND user_number = PRIOR user_number 

postgresql

select user_number,name from
(
 select alias1.*,
 row_number() over (partition by alias1.user_number order by rn desc) as leaf
from (
with RECURSIVE cte as
        (
        select a.user_number,cast(A.name as varchar(1000)),A.rn from (
        SELECT
                    u.user_number,
                    r.NAME,
                    ROW_NUMBER ( ) OVER ( PARTITION BY u.user_number ORDER BY ur.role_id ) RN
                FROM
                    ems_role r,
                    ( SELECT ur.user_id, ur.role_id FROM ems_user_role ur
                    UNION SELECT ur.user_id, ur.role_id FROM ems_user_device_role ur ) ur,
                    ems_user u
                WHERE
                    ur.user_id = u.ID
                    AND r.ID = ur.role_id   ) A where a.rn = 1
        union all
        select k.user_number,cast(c.name||‘,‘||k.name as varchar(1000)) as path,k.rn from (SELECT
                    u.user_number,
                    r.NAME,
                    ROW_NUMBER ( ) OVER ( PARTITION BY u.user_number ORDER BY ur.role_id) RN
                FROM
                    ems_role r,
                    ( SELECT ur.user_id, ur.role_id FROM ems_user_role ur
                    UNION SELECT ur.user_id, ur.role_id FROM ems_user_device_role ur ) ur,
                    ems_user u
                WHERE
                    ur.user_id = u.ID
                    AND r.ID = ur.role_id) k inner join cte c on c.RN + 1 = k.rn and c.user_number = k.user_number
        )
    select e.* from cte e where 1=1
) as alias1 where 1=1
) as  alias2 where leaf =1

原文地址：https://www.cnblogs.com/acme6/p/12516041.html