SQLServer 之 树查询

一、SqlServer树查询

1、使用公用表表达式（CTE）

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 table
    Where id = 6  -- 要查询的子 id
    Union All
    Select table.* From table, Tree
    Where Tree.parent = table.id
)
Select * From Tree;

--通过父节点查询子节点
With Tree As(
    Select * From table
    Where parent = 2  -- 要查询的父 id
    Union All
    Select table.* From table, Tree
    Where table.parent = Tree.id
)
Select * From Tree;

 2、自定义函数方式：

Create Function dbo.GetSubtreeInfo ( @parentId AS nvarchar(20) )
Returns @treeinfo table
(   FunctionId nvarchar(20) NOT NULL ,
    FunctionName nvarchar(50) NOT NULL,
    Url nvarchar(100),
    ParentId nvarchar(20) NOT NULL,
    OrderId nvarchar(20),
    [levels] [int] NOT NULL
)
As
Begin 
Declare @level As int
Select @level = 0
Insert Into @treeinfo
    Select FunctionId, FunctionName, Url, ParentId, OrderId, @level
    From SystemFunction
    Where ParentId  = @parentId
While @@ROWCOUNT > 0
Begin 

Set @level = @level + 1
Insert Into @treeinfo
    Select E.FunctionId, E.FunctionName, E.Url, E.ParentId, E.OrderId, @level
    From SystemFunction as E JOIN @treeinfo as T
    On E.ParentId = T.FunctionId and T.levels = @level - 1 

End
Return
End
drop function dbo.GetSubtreeInfo
select * from dbo.GetSubtreeInfo('F0000')