如何在 SQL Server 的表值函数中使用 CTE 语句

Question

我了解到某些版本的 Microsoft OLE DB Provider for SQL Server（主要在 Windows XP 上）不支持WITH 语句。因此，我决定将我的 SQL 语句移动到一个表值函数中，并从我的应用程序中调用它。现在，我被困住了。我应该如何将INSERT INTO 语句与WITH 一起使用？这是到目前为止我提供的代码，但 SQL Server 不喜欢它... :-(

CREATE FUNCTION GetDistributionTable 
(
    @IntID int,
    @TestID int,
    @DateFrom datetime,
    @DateTo datetime
)
RETURNS 
@Table_Var TABLE 
(
    [Count] int, 
    Result float
)
AS
BEGIN
INSERT INTO @Table_Var ([Count], Result) WITH T(Result)
     AS (SELECT ROUND(Result - AVG(Result) OVER(), 1)
         FROM RawResults WHERE IntID = @IntID AND DBTestID = @TestID AND Time >= @DateFrom AND Time <= @DateTo)
SELECT COUNT(*) AS [Count],
       Result
FROM   T
GROUP  BY Result

    RETURN 
END
GO

Answer 1

表值函数中 CTE 的语法为：

CREATE FUNCTION GetDistributionTable 
(
    @IntID int,
    @TestID int,
    @DateFrom datetime,
    @DateTo datetime
)
RETURNS TABLE
AS
RETURN  
(
    WITH cte AS
    (
        SELECT ROUND(Result - AVG(Result) OVER(), 1) Result
        FROM   RawResults 
        WHERE  IntID = @IntID 
        AND    DBTestID = @TestID 
        AND    Time >= @DateFrom 
        AND Time <= @DateTo    
    )

    SELECT  COUNT(*) AS [Count],
            Result
    FROM    cte
    GROUP  BY 
            Result
)
GO

如果可能，您也可以省略 CTE（WITH 语句），而是创建一个使用子查询的内联表值函数：

CREATE FUNCTION GetDistributionTable 
(
    @IntID int,
    @TestID int,
    @DateFrom datetime,
    @DateTo datetime
)
RETURNS TABLE
AS
RETURN  
(
    SELECT  COUNT(*) AS [Count],
            Result
    FROM    (
                 SELECT ROUND(Result - AVG(Result) OVER(), 1) Result
                 FROM   RawResults 
                 WHERE  IntID = @IntID 
                 AND    DBTestID = @TestID 
                 AND    Time >= @DateFrom 
                 AND Time <= @DateTo    
    ) t
    GROUP  BY 
            Result
)
GO

您的示例似乎使用了多语句 TVF（插入和选择），当您有选择时尝试使用内联 TVF，因为多语句 TVF 会阻止查询优化器选择更好的执行计划（解释了性能差异here)

Answer 2

CTE with if else in UDF 

USE [SchoolDB]
GO

/****** Object:  UserDefinedFunction [dbo].[GetDistributionTable]    Script Date: 24-08-2019 05:17:55 PM ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO





alter  FUNCTION [dbo].[GetDistributionTable] 
(
   @DepartmentName varchar(50) = 'Production'
)
RETURNS 
@Table_Var TABLE 
(   NUM int IDENTITY(1,1),
    [ParentEmployeeKey] int, 
    Result float
)
AS
BEGIN
Declare @Table_Vars table
(
    [ParentEmployeeKey] int, 
    Result float
);
insert into @Table_Vars([ParentEmployeeKey])
select COUNT(1) Result from 
        [SchoolDB].[dbo].[DimEmployee] where DepartmentName = @DepartmentName
if(@@rowcount >0)
begin
WITH T 
    AS (    
        select [ParentEmployeeKey],COUNT(1) Result from 
        [SchoolDB].[dbo].[DimEmployee] where DepartmentName = @DepartmentName
        group by [ParentEmployeeKey]
   )
  INSERT INTO @Table_Var ([ParentEmployeeKey], Result)
  SELECT COUNT(*) AS [Count],
       Result
  FROM   T
  GROUP  BY Result
end
else

 WITH T 
    AS (    
        select [ParentEmployeeKey],COUNT(1) Result from 
        [SchoolDB].[dbo].[DimEmployee] where DepartmentName = @DepartmentName
        group by [ParentEmployeeKey]
   )
  INSERT INTO @Table_Var ([ParentEmployeeKey], Result)
  SELECT COUNT(*) AS [Count],
       Result
  FROM   T
  GROUP  BY Result
  RETURN 
END



GO

Answer 3

喜欢这个..

CREATE FUNCTION GetDistributionTable 
(
    @IntID int,
    @TestID int,
    @DateFrom datetime,
    @DateTo datetime
)
RETURNS 
@Table_Var TABLE 
(
    [Count] int, 
    Result float
)
AS
BEGIN
  WITH T 
    AS (    
        select Ticket_Id,COUNT(1) Result from 
        Customer_Survey
        group by MemberID,SiteId,Ticket_Id
   )
  INSERT INTO @Table_Var ([Count], Result)
  SELECT COUNT(*) AS [Count],
       Result
  FROM   T
  GROUP  BY Result
  RETURN 
END
GO