PostgreSQL的递归查询(with recursive)，

PostgreSQL的递归查询(with recursive)，

[url]http://my.oschina.net/Kenyon/blog/55137[/url]


[color=red][b]示例[/b][/color]

with RECURSIVE cte as 
	( 
			select a.* from tb_sm_module a where module_id=0
			union all  
			select k.*  from tb_sm_module k inner join cte c on c.module_id = k.parent_id
	)select cte.* from cte;

[img]http://dl2.iteye.com/upload/attachment/0107/0746/f28bebac-0d06-3dab-996a-16243a948c2e.png[/img]

with RECURSIVE cte as
(
select a.module_id,cast(a.module_name as varchar(100)) from tb_sm_module a where module_id=0  
union all 
select k.module_id,cast(c.module_name||'>'||k.module_name as varchar(100)) as module_name  from tb_sm_module k inner join cte c on c.module_id = k.parent_id
)select module_id,module_name from cte ;

[img]http://dl2.iteye.com/upload/attachment/0107/0748/9251909d-0fc4-368d-8b9b-3a76f71f6314.png[/img]
这里有一个疑问,文什么把后面显示的层级名称改成module_id, 但不起到效果?


[b][color=red]两个方向的例子[/color][/b]

--向下查找
WITH RECURSIVE T AS(
		SELECT * FROM TB_SM_MODULE T1 WHERE MODULE_ID=1 --原始信息
		UNION AL]L
		SELECT T2.* FROM TB_SM_MODULE T2,T --附加信息
		WHERE T2.PARENT_ID = T.MODULE_ID  --附加信息的父亲等原始信息
)SELECT * FROM T


--向上查找
WITH RECURSIVE T AS(
		SELECT * FROM TB_SM_MODULE T1 WHERE MODULE_ID=1053  --原始信息
		UNION ALL
		SELECT T2.* FROM TB_SM_MODULE T2,T   --附加信息
		WHERE T2.MODULE_ID = T.PARENT_ID --原始信息的父亲等于附加信息
)SELECT * FROM T