¿Cómo se UNE con múltiples CTE?

Question

¿Cómo se UNE con múltiples CTE?

¿Cómo se usa UNION con múltiples Common Table Expressions?

Estoy tratando de reunir algunos números de resumen, pero no importa dónde ponga el ;, siempre recibo un error

SELECT  COUNT(*)
FROM    dbo.Decision_Data
UNION
SELECT  COUNT(DISTINCT Client_No)
FROM    dbo.Decision_Data
UNION
WITH    [Clients]
          AS ( SELECT   Client_No
               FROM     dbo.Decision_Data
               GROUP BY Client_No
               HAVING   COUNT(*) = 1
             )
    SELECT  COUNT(*) AS [Clients Single Record CTE]
    FROM    Clients;

ACTUALIZACIÓN: Aprecio en el ejemplo anterior que puedo mover el simple CTE al principio, pero tengo un número de CTEs que me gustaría UNION

39

sql-server common-table-expression union

Author: brett rogers, 2012-07-18

Source

2 answers

Puedes hacerlo así:

WITH    [Clients]
          AS ( SELECT   Client_No
               FROM     dbo.Decision_Data
               GROUP BY Client_No
               HAVING   COUNT(*) = 1
             ),
        [Clients2]
          AS ( SELECT   Client_No
               FROM     dbo.Decision_Data
               GROUP BY Client_No
               HAVING   COUNT(*) = 1
             )
SELECT  COUNT(*)
FROM    Clients
UNION
SELECT  COUNT(*)
FROM    Clients2;

11

Author: DaveShaw,
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2012-07-18 13:29:30

score 70 · Accepted Answer

Si está tratando de unir varios CTEs, primero debe declarar los CTEs y luego usarlos:

With Clients As
    (
    Select Client_No
    From dbo.Decision_Data
    Group By Client_No
    Having Count(*) = 1
    )
    , CTE2 As
    (
    Select Client_No
    From dbo.Decision_Data
    Group By Client_No
    Having Count(*) = 2
    )
Select Count(*)
From Decision_Data
Union
Select Count(Distinct Client_No)
From dbo.Decision_Data
Union
Select Count(*)
From Clients
Union
Select Count(*)
From CTE2;

Incluso puedes usar un CTE de otro:

With Clients As
        (
        Select Client_No
        From dbo.Decision_Data
        Group By Client_No
        Having Count(*) = 1
        )
        , CTE2FromClients As
        (
        Select Client_No
        From Clients
        )
    Select Count(*)
    From Decision_Data
    Union
    Select Count(Distinct Client_No)
    From dbo.Decision_Data
    Union
    Select Count(*)
    From Clients
    Union
    Select Count(*)
    From CTE2FromClients;

CON common_table_expression (Transact-SQL)