공통 테이블 표현식에 대해 중첩 된 WITH 절을 작성할 수 있습니까?

공통 테이블 표현식에 대해 중첩 된 WITH 절을 작성할 수 있습니까?

---

WITH y AS (
    WITH x AS (
        SELECT * FROM MyTable
    )
    SELECT * FROM x
)
SELECT * FROM y

이런 식으로 작동합니까? 나는 그것을 일찍 시도했지만 그것을 작동시킬 수 없었다.

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엄격하게 중첩되지는 않지만 공통 테이블 표현식을 사용하여 후속 쿼리에서 이전 쿼리를 재사용 할 수 있습니다.

이를 위해 찾고자하는 진술서의 형태는 다음과 같습니다.

WITH x AS 
(
    SELECT * FROM MyTable
), 
y AS 
(
    SELECT * FROM x
)
SELECT * FROM y

---

재귀 쿼리라고하는 다음을 수행 할 수 있습니다.

WITH y
AS
(
  SELECT x, y, z
  FROM MyTable
  WHERE [base_condition]

  UNION ALL

  SELECT x, y, z
  FROM MyTable M
  INNER JOIN y ON M.[some_other_condition] = y.[some_other_condition]
)
SELECT *
FROM y

이 기능이 필요하지 않을 수 있습니다. 쿼리를 더 잘 구성하기 위해 다음을 수행했습니다.

WITH y 
AS
(
  SELECT * 
  FROM MyTable
  WHERE [base_condition]
),
x
AS
(
  SELECT * 
  FROM y
  WHERE [something_else]
)
SELECT * 
FROM x

---

포함은 작동하지 않지만 연속적으로 작동합니다

;WITH A AS(
...
),
B AS(
...
)
SELECT *
FROM A
UNION ALL
SELECT *
FROM B

편집 구문을 수정했습니다 ...

또한 다음 예제를 살펴보십시오

SQLFiddle 데모

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These answers are pretty good, but as far as getting the items to order properly, you'd be better off looking at this article http://dataeducation.com/dr-output-or-how-i-learned-to-stop-worrying-and-love-the-merge

Here's an example of his query.

WITH paths AS ( 
    SELECT 
        EmployeeID, 
        CONVERT(VARCHAR(900), CONCAT('.', EmployeeID, '.')) AS FullPath 
    FROM EmployeeHierarchyWide 
    WHERE ManagerID IS NULL

    UNION ALL

    SELECT 
        ehw.EmployeeID, 
        CONVERT(VARCHAR(900), CONCAT(p.FullPath, ehw.EmployeeID, '.')) AS FullPath 
    FROM paths AS p 
        JOIN EmployeeHierarchyWide AS ehw ON ehw.ManagerID = p.EmployeeID 
) 
SELECT * FROM paths order by FullPath

---

we can create nested cte.please see the below cte in example

;with cte_data as 
(
Select * from [HumanResources].[Department]
),cte_data1 as
(
Select * from [HumanResources].[Department]
)

select * from cte_data,cte_data1

---

I was trying to measure the time between events with the exception of what one entry that has multiple processes between the start and end. I needed this in the context of other single line processes.

I used a select with an inner join as my select statement within the Nth cte. The second cte I needed to extract the start date on X and end date on Y and used 1 as an id value to left join to put them on a single line.

Works for me, hope this helps.

cte_extract
as 
(
    select ps.Process as ProcessEvent
        , ps.ProcessStartDate 
        , ps.ProcessEndDate 
        -- select strt.*
    from dbo.tbl_some_table ps 
    inner join (select max(ProcessStatusId) ProcessStatusId 
                    from dbo.tbl_some_table 
                where Process = 'some_extract_tbl' 
                and convert(varchar(10), ProcessStartDate, 112) < '29991231'
                ) strt on strt.ProcessStatusId = ps.ProcessStatusID
), 
cte_rls
as 
(
    select 'Sample' as ProcessEvent, 
     x.ProcessStartDate, y.ProcessEndDate  from (
    select 1 as Id, ps.Process as ProcessEvent
        , ps.ProcessStartDate 
        , ps.ProcessEndDate
        -- select strt.*
    from dbo.tbl_some_table ps 
    inner join (select max(ProcessStatusId) ProcessStatusId 
                    from dbo.tbl_some_table 
                where Process = 'XX Prcss' 
                and convert(varchar(10), ProcessStartDate, 112) < '29991231'
                ) strt on strt.ProcessStatusId = ps.ProcessStatusID
    ) x
    left join (
        select 1 as Id, ps.Process as ProcessEvent
            , ps.ProcessStartDate 
            , ps.ProcessEndDate
            -- select strt.*
        from dbo.tbl_some_table ps 
        inner join (select max(ProcessStatusId) ProcessStatusId
                    from dbo.tbl_some_table 
                    where Process = 'YY Prcss Cmpltd' 
                    and convert(varchar(10), ProcessEndDate, 112) < '29991231'
                    ) enddt on enddt.ProcessStatusId = ps.ProcessStatusID
            ) y on y.Id = x.Id 
),

.... other ctes

참고URL : https://stackoverflow.com/questions/1413516/can-you-create-nested-with-clauses-for-common-table-expressions