我有一个自引用表 Foo
[Id] int NOT NULL,
[ParentId] int NULL, --Foreign key to [Id]
[Type] char(1) NOT NULL
[Id]
是聚簇主键,索引位于 [ParentId]
和 [Type]
列。假设层次结构的最大深度为 1(子节点不能有子节点)。
我想获得满足以下条件的所有 Foo 行:
以下使用 JOIN 的查询返回所需的结果,但性能很差
SELECT DISTINCT [Main].*
FROM Foo AS [Main]
--[Main] may not be root node
LEFT OUTER JOIN Foo AS [Parent]
ON [Parent].[Id] = [Main].[ParentId]
--Must have a B in tree
INNER JOIN Foo AS [NodeB]
ON (
[NodeB].[Pid] = [Main].[Pid] --Sibling
OR [NodeB].[ParentId] = [Main].[Id] --Child
OR [NodeB].[Id] = [Parent].[Id] --Parent
)
AND [NodeB].[Type] = 'B'
--Must have a C or D in tree
INNER JOIN Foo AS [NodeCD]
ON (
[NodeCD].[Pid] = [Main].[Pid] --Sibling
OR [NodeCD].[ParentId] = [Main].[Id] --Child
OR [NodeCD].[Id] = [Parent].[Id] --Parent
)
AND [NodeCD].[Type] IN ('C', 'D')
WHERE [Main].[Type] = 'A'
从实际执行计划限制为仅查看 650,000 行中的前 10,000
如果我从查询中删除 --Parent 行
OR [NodeB].[Id] = [Parent].[Id] --Parent
OR [NodeCD].[Id] = [Parent].[Id] --Parent
然后执行几乎是瞬间的,但它错过了 A 是 child 并且只有一个兄弟的情况
Misses this: Catches this:
B B
├A ├A
└C ├B
└C
我试图想出一个 CTE 来做到这一点,因为它在性能方面似乎更有希望,但我一直无法弄清楚如何排除那些不满足标准的树。
到目前为止的 CTE
WITH [Parent] AS
(
SELECT *
FROM [Foo]
WHERE [ParentId] IS NULL
UNION ALL
SELECT [Child].*
FROM Foo AS [Child]
JOIN [Parent]
ON [Child].[ParentId] = [Parent].Id
WHERE [Child].[Type] = 'P'
UNION ALL
SELECT [ChildCD].*
FROM Foo AS [ChildCD]
JOIN [Parent]
ON [ChildCD].[ParentId] = [Parent].Id
WHERE [ChildCD].[Type] IN ('C', 'D')
)
SELECT *
FROM [Parent]
WHERE [Type] = 'I';
但是,如果我尝试添加 Sibling-Child-Parent OR 语句,则会达到最大递归级别 100。
SQL Fiddle with test data
最佳答案
被检查的节点是根节点的情况与它是子节点的情况有足够的区别,因此您最好分别查询两者并形成 UNION ALL
两组中。但是,您可以使用公用表表达式进行简化,该表达式标识包含您要查找的节点的那些树。总的来说,这可能是这样的:
WITH [TargetFamilies] AS (
SELECT
COALESCE(ParentId, Id) AS FamilyId
FROM Foo
GROUP BY COALESCE(ParentId, Id)
HAVING
COUNT(CASE Type WHEN 'B' THEN 1 END) > 0
AND COUNT(CASE Type WHEN 'C' THEN 1 WHEN 'D' THEN 1 END) > 0
)
-- root nodes
SELECT [Main].*
FROM
Foo AS [Main]
JOIN [TargetFamilies] ON [Main].Id = [TargetFamilies].FamilyId
WHERE
[Main].Type = 'A'
UNION ALL
-- child nodes
SELECT
[Main].*
FROM
Foo AS [Main]
JOIN [TargetFamilies] ON [Main].ParentId = [TargetFamilies].FamilyId
WHERE
[Main].Type = 'A'
关于sql - 根据相关节点从层次结构中选择行,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/29496352/