SqlServer 递归查询树

递归关于进行树形结构的查询：

1、简单的树形结构代码。

-- with一个临时表(括号中是你要查询的列名)
with temp(ID,PID,Name,curLevel)
as
(
--1：初始查询（这里的PID=-1 在我的数据中是最底层的根节点）
select ID,PID,Name,1 as level from dbo.T_ACL_OU 
where Deleted = 0 and PID = -1     
union all
--2：递归条件
select a.ID,a.PID,a.Name, b.curLevel+1from T_ACL_OU a   --3：这里的临时表和原始数据表都必须使用别名，不然递归的时候不知道查询的是那个表的列
inner join
temp b
on ( a.PID=b.id)  --这个关联关系很重要，一定要理解一下谁是谁的父节点
)
select * from temp   --4：递归完成后 一定不要少了这句查询语句 否则会报错

2、带缩进的树形机构

with temp(ID,PID,Name,curLevel)
as
(
--初始查询
select ID,PID,Name,1 as curLevel from dbo.T_ACL_OU 
where Deleted = 0 and PID = -1     
union all
--递归条件
select a.ID,a.PID, 
convert(nvarchar(100),CONVERT(nvarchar(100), REPLICATE ('    ', b.curLevel+1)+a.Name)) as Name , b.curLevel+1 
  --这里的 REPLICATE函数非常重要，用于缩进空格用。不懂得可以在SQLserver中选中后按F1键
from T_ACL_OU a 
inner join
temp b
on ( a.PID=b.id)
)
select ID,PID,Name,curLevel from temp

3、查询是否有子节点

with temp(ID,PID,HandNo,Name,curLevel,pLevel,haveChild)
as
(
--初始查询
select ID,PID,HandNo,Name,1 as level,0 as pLevel,1 as haveChild from dbo.T_ACL_OU 
where Deleted = 0 and PID = -1     
union all
--递归条件
select a.ID,a.PID,a.HandNo,a.Name, b.curLevel+1,b.curLevel,haveChild 
= (case when exists(select 1 from T_ACL_OU where T_ACL_OU.PID=a.id) then 1 else 0 end)
--(select 1 from T_ACL_OU where exists(select 1 from T_ACL_OU where a.PID=b.id)) 
from T_ACL_OU a 
inner join
temp b
on ( a.PID=b.id)
)
select * from temp order by pLevel
--------------------------------------------------------


with temp(sstation,ParentStation,SStationName,curLevel,pLevel,haveChild)
as
(
--初始查询
select sstation,ParentStation,SStationName,1 as level,0 as pLevel,1 as haveChild from [dbo].[Weather_Station] 
where ParentStation='4300000' 
union all
--递归条件
select a.sstation,a.ParentStation,a.SStationName, b.curLevel+1,b.curLevel,haveChild 
= (case when exists(select 1 from [dbo].[Weather_Station]  where ParentStation=a.sstation) then 1 else 0 end)
--(select 1 from [dbo].[Weather_Station]  where exists(select 1 from [dbo].[Weather_Station] where a.ParentStation=b.sstation)) 
from [dbo].[Weather_Station]  a 
inner join
temp b
on ( a.ParentStation=b.sstation)
)
select * from temp order by pLevel

这3段代码可以直接复制使用，修改一下表名和要查询的列名基本上都是通用的。