J. Using multiple anchor and recursive members
The following example uses multiple anchor and recursive members to return all the ancestors of a specified person. A table is created and values inserted to establish the family genealogy returned by the recursive CTE.-- Genealogy table
IF OBJECT_ID('Person','U') IS NOT NULL DROP TABLE Person;
GO
CREATE TABLE Person(ID int, Name varchar(30), Mother int, Father int);
GO
INSERT Person VALUES(1, 'Sue', NULL, NULL);
INSERT Person VALUES(2, 'Ed', NULL, NULL);
INSERT Person VALUES(3, 'Emma', 1, 2);
INSERT Person VALUES(4, 'Jack', 1, 2);
INSERT Person VALUES(5, 'Jane', NULL, NULL);
INSERT Person VALUES(6, 'Bonnie', 5, 4);
INSERT Person VALUES(7, 'Bill', 5, 4);
GO
-- Create the recursive CTE to find all of Bonnie's ancestors.
WITH Generation (ID) AS
(
-- First anchor member returns Bonnie's mother.
SELECT Mother
FROM Person
WHERE Name = 'Bonnie'
UNION
-- Second anchor member returns Bonnie's father.
SELECT Father
FROM Person
WHERE Name = 'Bonnie'
UNION ALL
-- First recursive member returns male ancestors of the previous generation.
SELECT Person.Father
FROM Generation, Person
WHERE Generation.ID=Person.ID
UNION ALL
-- Second recursive member returns female ancestors of the previous generation.
SELECT Person.Mother
FROM Generation, Person
WHERE Generation.ID=Person.ID
)
SELECT Person.ID, Person.Name, Person.Mother, Person.Father
FROM Generation, Person
WHERE Generation.ID = Person.ID;
GO
问题是这样的,请大家把CTE的十种应用例子的每帖所涉及的例子讲解一番,其应用范围及和其它CTE实例的区别
The following example uses multiple anchor and recursive members to return all the ancestors of a specified person. A table is created and values inserted to establish the family genealogy returned by the recursive CTE.-- Genealogy table
IF OBJECT_ID('Person','U') IS NOT NULL DROP TABLE Person;
GO
CREATE TABLE Person(ID int, Name varchar(30), Mother int, Father int);
GO
INSERT Person VALUES(1, 'Sue', NULL, NULL);
INSERT Person VALUES(2, 'Ed', NULL, NULL);
INSERT Person VALUES(3, 'Emma', 1, 2);
INSERT Person VALUES(4, 'Jack', 1, 2);
INSERT Person VALUES(5, 'Jane', NULL, NULL);
INSERT Person VALUES(6, 'Bonnie', 5, 4);
INSERT Person VALUES(7, 'Bill', 5, 4);
GO
-- Create the recursive CTE to find all of Bonnie's ancestors.
WITH Generation (ID) AS
(
-- First anchor member returns Bonnie's mother.
SELECT Mother
FROM Person
WHERE Name = 'Bonnie'
UNION
-- Second anchor member returns Bonnie's father.
SELECT Father
FROM Person
WHERE Name = 'Bonnie'
UNION ALL
-- First recursive member returns male ancestors of the previous generation.
SELECT Person.Father
FROM Generation, Person
WHERE Generation.ID=Person.ID
UNION ALL
-- Second recursive member returns female ancestors of the previous generation.
SELECT Person.Mother
FROM Generation, Person
WHERE Generation.ID=Person.ID
)
SELECT Person.ID, Person.Name, Person.Mother, Person.Father
FROM Generation, Person
WHERE Generation.ID = Person.ID;
GO
问题是这样的,请大家把CTE的十种应用例子的每帖所涉及的例子讲解一番,其应用范围及和其它CTE实例的区别
也是就查询Bonnie的所有祖先。
set nocount on ;
if not object_id('Tempdb..#T') is null
drop table #T
Go
Create table #T([Num] int,[Name] nvarchar(1))
Insert #T
select 1,N'A' union all
select 1,N'A' union all
select 2,N'B' union all
select 2,N'B'go--Delete
;with CTE as
(select row=row_number()over(partition by [Num],[Name] order by (select 1)),[Num],[Name] from #T)
delete CTE where row>1select * from #T
/*
Num Name
----------- ----
1 A
2 B
*/--insert
;with CTE as
(select [Num],[Name] from #T)
insert CTE
select * from CTEselect * from #T
/*
Num Name
----------- ----
1 A
1 A
2 B
2 B
*/--update
;with CTE as
(select row=row_number()over(partition by [Num] order by (select 1)),[Num],[Name] from #T)
update CTE
set [Num]=CTE.rowselect * from #T
/*
Num Name
----------- ----
1 A
2 A
1 B
2 B
*/
/*一、直接CTE,然后引用全部CTE列,CTE行(最基础的),非递归CTE*/
USE AdventureWorks;
GO
WITH DirReps(ManagerID, DirectReports) AS
(
SELECT ManagerID, COUNT(*)
FROM HumanResources.Employee AS e
WHERE ManagerID IS NOT NULL
GROUP BY ManagerID
)
SELECT ManagerID, DirectReports
FROM DirReps
ORDER BY ManagerID;/*二、直接CTE,然后引用全部CTE列,部分CTE行,非递归CTE*/
WITH DirReps (Manager, DirectReports) AS
(
SELECT ManagerID, COUNT(*) AS DirectReports
FROM HumanResources.Employee
GROUP BY ManagerID
)
SELECT AVG(DirectReports) AS [Average Number of Direct Reports]
FROM DirReps
WHERE DirectReports>= 2 ;
GO
/*三、直接CTE,然后引用部分CTE列及外联表的列,属于非递归CTE*/
USE AdventureWorks;
GO
WITH Sales_CTE (SalesPersonID, NumberOfOrders, MaxDate)
AS
(
SELECT SalesPersonID, COUNT(*), MAX(OrderDate)
FROM Sales.SalesOrderHeader
GROUP BY SalesPersonID
)
SELECT E.EmployeeID, OS.NumberOfOrders, OS.MaxDate,
E.ManagerID, OM.NumberOfOrders, OM.MaxDate
FROM HumanResources.Employee AS E
JOIN Sales_CTE AS OS
ON E.EmployeeID = OS.SalesPersonID
LEFT OUTER JOIN Sales_CTE AS OM
ON E.ManagerID = OM.SalesPersonID
ORDER BY E.EmployeeID;
GO
/*四、预定义CTE,集合运算符联接起来递归CTE,然后引用全部CTE列,全部CTE行,属于递归CTE*/
USE AdventureWorks;
GO
WITH DirectReports(ManagerID, EmployeeID, EmployeeLevel) AS
(
SELECT ManagerID, EmployeeID, 0 AS EmployeeLevel
FROM HumanResources.Employee
WHERE ManagerID IS NULL
UNION ALL
SELECT e.ManagerID, e.EmployeeID, EmployeeLevel + 1
FROM HumanResources.Employee e
INNER JOIN DirectReports d
ON e.ManagerID = d.EmployeeID
)
SELECT ManagerID, EmployeeID, EmployeeLevel
FROM DirectReports ;
GO
/*五、预定义CTE,集合运算符联接起来递归CTE,然后引用全部CTE列,部分CTE行,属于递归CTE*/
USE AdventureWorks;
GO
WITH DirectReports(ManagerID, EmployeeID, EmployeeLevel) AS
(
SELECT ManagerID, EmployeeID, 0 AS EmployeeLevel
FROM HumanResources.Employee
WHERE ManagerID IS NULL
UNION ALL
SELECT e.ManagerID, e.EmployeeID, EmployeeLevel + 1
FROM HumanResources.Employee e
INNER JOIN DirectReports d
ON e.ManagerID = d.EmployeeID
)
SELECT ManagerID, EmployeeID, EmployeeLevel
FROM DirectReports
WHERE EmployeeLevel <= 2 ;
GO
/*六、预定义CTE,集合运算符联接起来递归CTE,然后分组引用部分CTE列,全部CTE行,属于递归CTE*/
USE AdventureWorks;
GO
WITH DirectReports(Name, Title, EmployeeID, EmployeeLevel, Sort)
AS (SELECT CONVERT(varchar(255), c.FirstName + ' ' + c.LastName),
e.Title,
e.EmployeeID,
1,
CONVERT(varchar(255), c.FirstName + ' ' + c.LastName)
FROM HumanResources.Employee AS e
JOIN Person.Contact AS c ON e.ContactID = c.ContactID
WHERE e.ManagerID IS NULL
UNION ALL
SELECT CONVERT(varchar(255), REPLICATE ('| ' , EmployeeLevel) +
c.FirstName + ' ' + c.LastName),
e.Title,
e.EmployeeID,
EmployeeLevel + 1,
CONVERT (varchar(255), RTRIM(Sort) + '| ' + FirstName + ' ' +
LastName)
FROM HumanResources.Employee as e
JOIN Person.Contact AS c ON e.ContactID = c.ContactID
JOIN DirectReports AS d ON e.ManagerID = d.EmployeeID
)
SELECT EmployeeID, Name, Title, EmployeeLevel
FROM DirectReports
ORDER BY Sort;
GO/*七、预定义CTE,集合运算符联接起来递归CTE,使用 MAXRECURSION 来防止不合理的递归 CTE 进入无限循环*/
USE AdventureWorks;
GO
--Creates an infinite loop
WITH cte (EmployeeID, ManagerID, Title) as
(
SELECT EmployeeID, ManagerID, Title
FROM HumanResources.Employee
WHERE ManagerID IS NOT NULL
UNION ALL
SELECT cte.EmployeeID, cte.ManagerID, cte.Title
FROM cte
JOIN HumanResources.Employee AS e
ON cte.ManagerID = e.EmployeeID
)
--Uses MAXRECURSION to limit the recursive levels to 2
SELECT EmployeeID, ManagerID, Title
FROM cte
OPTION (MAXRECURSION 2);/*八、直接CTE,然后引用CTE自身内联*/
USE AdventureWorks;
GO
WITH Parts(AssemblyID, ComponentID, PerAssemblyQty, EndDate, ComponentLevel) AS
(
SELECT b.ProductAssemblyID, b.ComponentID, b.PerAssemblyQty,
b.EndDate, 0 AS ComponentLevel
FROM Production.BillOfMaterials AS b
WHERE b.ProductAssemblyID = 800
AND b.EndDate IS NULL
UNION ALL
SELECT bom.ProductAssemblyID, bom.ComponentID, p.PerAssemblyQty,
bom.EndDate, ComponentLevel + 1
FROM Production.BillOfMaterials AS bom
INNER JOIN Parts AS p
ON bom.ProductAssemblyID = p.ComponentID
AND bom.EndDate IS NULL
)
SELECT AssemblyID, ComponentID, Name, PerAssemblyQty, EndDate,
ComponentLevel
FROM Parts AS p
INNER JOIN Production.Product AS pr
ON p.ComponentID = pr.ProductID
ORDER BY ComponentLevel, AssemblyID, ComponentID;
GO/*九、递归CTE用于UPDATE FROM更新子句*/
USE AdventureWorks;
GO
WITH DirectReports(EmployeeID, NewVacationHours, EmployeeLevel)
AS
(SELECT e.EmployeeID, e.VacationHours, 1
FROM HumanResources.Employee AS e
WHERE e.ManagerID = 12
UNION ALL
SELECT e.EmployeeID, e.VacationHours, EmployeeLevel + 1
FROM HumanResources.Employee as e
JOIN DirectReports AS d ON e.ManagerID = d.EmployeeID
)
UPDATE HumanResources.Employee
SET VacationHours = VacationHours * 1.25
FROM HumanResources.Employee AS e
JOIN DirectReports AS d ON e.EmployeeID = d.EmployeeID;
GO/*十、直接CTE,用CTE列作为条件进行引用*/
-- Genealogy table
IF OBJECT_ID('Person','U') IS NOT NULL DROP TABLE Person;
GO
CREATE TABLE Person(ID int, Name varchar(30), Mother int, Father int);
GO
INSERT Person VALUES(1, 'Sue', NULL, NULL);
INSERT Person VALUES(2, 'Ed', NULL, NULL);
INSERT Person VALUES(3, 'Emma', 1, 2);
INSERT Person VALUES(4, 'Jack', 1, 2);
INSERT Person VALUES(5, 'Jane', NULL, NULL);
INSERT Person VALUES(6, 'Bonnie', 5, 4);
INSERT Person VALUES(7, 'Bill', 5, 4);
GO
-- Create the recursive CTE to find all of Bonnie's ancestors.
WITH Generation (ID) AS
(
-- First anchor member returns Bonnie's mother.
SELECT Mother
FROM Person
WHERE Name = 'Bonnie'
UNION
-- Second anchor member returns Bonnie's father.
SELECT Father
FROM Person
WHERE Name = 'Bonnie'
UNION ALL
-- First recursive member returns male ancestors of the previous generation.
SELECT Person.Father
FROM Generation, Person
WHERE Generation.ID=Person.ID
UNION ALL
-- Second recursive member returns female ancestors of the previous generation.
SELECT Person.Mother
FROM Generation, Person
WHERE Generation.ID=Person.ID
)
SELECT Person.ID, Person.Name, Person.Mother, Person.Father
FROM Generation, Person
WHERE Generation.ID = Person.ID;
GO
最后总结一下
其中的不同点主要有一下几个方面:--1、CTE的定义:
--1)直接CTE
WITH Generation (ID) AS (SELECT Mother FROM Person WHERE Name = 'Bonnie')
--2)预定义CTE
WITH cte (EmployeeID, ManagerID, Title) as
(
SELECT EmployeeID, ManagerID, Title
FROM HumanResources.Employee
WHERE ManagerID IS NOT NULL
UNION ALL
SELECT cte.EmployeeID, cte.ManagerID, cte.Title
FROM cte
JOIN HumanResources.Employee AS e
ON cte.ManagerID = e.EmployeeID
)
--ps:通俗讲就是cte里面用到了cte--2、引用方式:
--1)直接引用:
WITH Generation (ID) AS (SELECT Mother FROM Person WHERE Name = 'Bonnie')
select ID from Generation
--2)复核引用:
WITH Generation (ID) AS (SELECT Mother FROM Person WHERE Name = 'Bonnie')
SELECT Person.ID, Person.Name, Person.Mother, Person.Father
FROM Generation, Person
WHERE Generation.ID = Person.ID;--3、CTE列的使用
--1)引用全部列
WITH Generation (ID) AS (SELECT Mother FROM Person WHERE Name = 'Bonnie')
select ID from Generation
--2)分组显示
WITH DirectReports(Name, Title, EmployeeID, EmployeeLevel, Sort)
AS (SELECT * from
)
SELECT EmployeeID, Name, Title, EmployeeLevel
FROM DirectReports
ORDER BY Sort;
--3)引用部分列
WITH DirectReports(Name, Title, EmployeeID, EmployeeLevel, Sort)
AS (SELECT * from
)
SELECT sum(EmployeeID)
FROM DirectReports --4、CTE行的使用,就是有的时候使用where,有的时候没有where
--例如一和二的区别就是多了where条件 和 CTE列的使用 --5、有两个特殊的就是7和9,一个避免死循环的,一个是应用于update from子句
-- Genealogy table
IF OBJECT_ID('Person','U') IS NOT NULL DROP TABLE Person;
GO
CREATE TABLE Person(ID int, Name varchar(30), Mother int, Father int);
GO
INSERT Person VALUES(1, 'Sue', NULL, NULL);
INSERT Person VALUES(2, 'Ed', NULL, NULL);
INSERT Person VALUES(3, 'Emma', 1, 2);
INSERT Person VALUES(4, 'Jack', 1, 2);
INSERT Person VALUES(5, 'Jane', NULL, NULL);
INSERT Person VALUES(6, 'Bonnie', 5, 4);
INSERT Person VALUES(7, 'Bill', 5, 4);
GO
-- Create the recursive CTE to find all of Bonnie's ancestors.
WITH Generation (ID) AS
(
-- First anchor member returns Bonnie's mother.
SELECT Mother
FROM Person
WHERE Name = 'Bonnie'
UNION
-- Second anchor member returns Bonnie's father.
SELECT Father
FROM Person
WHERE Name = 'Bonnie'
UNION ALL
-- First recursive member returns male ancestors of the previous generation.
SELECT Person.Father
FROM Generation, Person
WHERE Generation.ID=Person.ID
UNION ALL
-- Second recursive member returns female ancestors of the previous generation.
SELECT Person.Mother
FROM Generation, Person
WHERE Generation.ID=Person.ID
)
SELECT Person.ID, Person.Name, Person.Mother, Person.Father
FROM Generation, Person
WHERE Generation.ID = Person.ID;GO
-- Genealogy table
IF OBJECT_ID('Person','U') IS NOT NULL DROP TABLE Person;
GO
CREATE TABLE Person(ID int, Name varchar(30), Mother int, Father int);
GO
INSERT Person VALUES(1, 'Sue', NULL, NULL);
INSERT Person VALUES(2, 'Ed', NULL, NULL);
INSERT Person VALUES(3, 'Emma', 1, 2);
INSERT Person VALUES(4, 'Jack', 1, 2);
INSERT Person VALUES(5, 'Jane', NULL, NULL);
INSERT Person VALUES(6, 'Bonnie', 5, 4);
INSERT Person VALUES(7, 'Bill', 5, 4);
GO
-- Create the recursive CTE to find all of Bonnie's ancestors.
WITH Generation (ID) AS
(
-- First anchor member returns Bonnie's mother.
SELECT Mother
FROM Person
WHERE Name = 'Bonnie'
UNION
-- Second anchor member returns Bonnie's father.
SELECT Father
FROM Person
WHERE Name = 'Bonnie'
UNION ALL
-- First recursive member returns male ancestors of the previous generation.
SELECT Person.Father
FROM Generation, Person
WHERE Generation.ID=Person.ID
UNION ALL
-- Second recursive member returns female ancestors of the previous generation.
SELECT Person.Mother
FROM Generation, Person
WHERE Generation.ID=Person.ID
)
SELECT Person.ID, Person.Name, Person.Mother, Person.Father
FROM Generation, Person
WHERE Generation.ID = Person.ID;GO 引用 7 楼 dobear_0922 的回复:
先查询出Bonnie的父亲、母亲,然后查询Bonnie的父亲的父母、Bonnie的母亲的父母,
也是就查询Bonnie的所有祖先。
不对呀,红色部分^
-- Genealogy table
IF OBJECT_ID('Person','U') IS NOT NULL DROP TABLE Person;
GO
CREATE TABLE Person(ID int, Name varchar(30), Mother int, Father int);
GO
INSERT Person VALUES(1, 'Sue', NULL, NULL);
INSERT Person VALUES(2, 'Ed', NULL, NULL);
INSERT Person VALUES(3, 'Emma', 1, 2);
INSERT Person VALUES(4, 'Jack', 1, 2);
INSERT Person VALUES(5, 'Jane', NULL, NULL);
INSERT Person VALUES(6, 'Bonnie', 5, 4);
INSERT Person VALUES(7, 'Bill', 5, 4);
GO-- Create the recursive CTE to find all of Bonnie's ancestors.
WITH Generation (ParentID) AS --这里改了
(
-- First anchor member returns Bonnie's mother.
SELECT Mother
FROM Person
WHERE Name = 'Bonnie'
UNION
-- Second anchor member returns Bonnie's father.
SELECT Father
FROM Person
WHERE Name = 'Bonnie'
UNION ALL
-- First recursive member returns male ancestors of the previous generation.
SELECT Person.Father
FROM Generation, Person
WHERE Generation.ParentID=Person.ID --这里改了
UNION ALL
-- Second recursive member returns female ancestors of the previous generation.
SELECT Person.Mother
FROM Generation, Person
WHERE Generation.ParentID=Person.ID --这里改了
)
SELECT Person.ID, Person.Name, Person.Mother, Person.Father
FROM Generation, Person
WHERE Generation.ParentID = Person.ID;--这里改了
GO