SQL Server 树形表非循环递归查询

很多人可能想要查询整个树形表关联的内容都会通过循环递归来查...事实上在微软在SQL2005或以上版本就能用别的语法进行查询，下面是示例。

--通过子节点查询父节点
WITH
TREE AS(
    SELECT * FROM Areas
    WHERE id = 6  -- 要查询的子 id
    UNION ALL
    SELECT Areas.* FROM Areas, TREE
    WHERE TREE.PId = Areas.Id
)
SELECT Area FROM TREE

--通过父节点查询子节点
WITH
TREE AS(
    SELECT * FROM Areas
    WHERE id = 7  -- 要查询的子 id
    UNION ALL
    SELECT Areas.* FROM Areas, TREE
    WHERE TREE.Id = Areas.PId
)
SELECT Area FROM TREE

通过子节点查询父节点查询结果为：

修改代码为

--通过子节点查询父节点
declare @area varchar(8000);
WITH
TREE AS(
    SELECT * FROM Areas
    WHERE id = 6  -- 要查询的子 id
    UNION ALL
    SELECT Areas.* FROM Areas, TREE
    WHERE TREE.PId = Areas.Id
)
select @area=isnull(@area,'')+Area from Tree order by id
select Area= @area
则结果为：中国北京市丰台区

根据以上可以将这段代码封装为一个存储过程

-----存储过程，递归获取树形地区表字符串
if exists (select * from sysobjects where name='SP_GetAreaStr')
drop proc SP_GetAreaStr
go
create procedure SP_GetAreaStr
@id int
as
declare @area varchar(8000)
begin
WITH
TREE AS(
    SELECT * FROM Areas
    WHERE id = @id  -- 要查询的子 id
    UNION ALL
    SELECT Areas.* FROM Areas, TREE
    WHERE TREE.PId = Areas.Id
)
select @area=isnull(@area,'')+Area from Tree order by id
select Area= @area
end
go
--exec sp_helptext 'SP_GetAreaStr'
--go
exec SP_GetAreaStr 28
go

查询结果：中国安徽省宿州市灵璧县

所用表结构：