總結兩個函數調用的結果SQL Server

Question

我想高效地總結兩個函數調用的結果並在第三列中顯示值。這裏是語法我有...

SELECT TOP (1000) Region, 
dbo.fn_Function1(Code, 2016) AS [Highest Students], 
dbo.fn_Function2(Code, 2016) AS [Highest Schools], 
dbo.fn_Function3(Code, 2016) AS [Average Students], 
dbo.fn_Function4(Code, 2016) AS [Average Schools], 
dbo.fn_Calculator(0,0) as [Total Students], 
dbo.fn_Calculator(0,0) as [Total Schools] 
From myTable 

fn_calculator應該採取作爲參數（最高學生+平均學生）的價值和總結他們。同樣，對於（最高學校+平均學校）

我寧可不重新在計算器功能的參數內再次運行功能。我現在只有（0,0）作爲佔位符。我試圖加載計算器是這樣的：但它不能識別的列名：

dbo.fn_Calculator([Highest Students], [Average Students]) 

Answer 1

最有效的方法是避免功能。但您可以使用子查詢或CTE：

WITH Calcs AS 
(
    SELECT Region, 
    dbo.fn_Function1(Code, 2016) AS [Highest Students], 
    dbo.fn_Function2(Code, 2016) AS [Highest Schools], 
    dbo.fn_Function3(Code, 2016) AS [Average Students], 
    dbo.fn_Function4(Code, 2016) AS [Average Schools], 
    From myTable 
) 
SELECT TOP 1000 
    [Highest Students], 
    [Highest Schools], 
    [Average Students], 
    [Average Schools], 
    dbo.fn_Calculator([Highest Students], [Average Students]) as [Total Students], 
    dbo.fn_Calculator([Highest Schools], [Average Schools]) as [Total Schools] 
FROM Calcs 

Answer 2

你可以做到這一點

select top (1000) 
    Region, 
    calc.[Highest Students], 
    calc.[Highest Schools], 
    calc.[Average Students], 
    calc.[Average Schools], 
    dbo.fn_Calculator(calc.[Highest Students], calc.[Average Students]) as [Total Students], 
    dbo.fn_Calculator(calc.[Highest Schools], calc.[Average Schools]) as [Total Schools] 
From myTable as t 
    outer apply (select 
     dbo.fn_Function1(Code, 2016) AS [Highest Students], 
     dbo.fn_Function2(Code, 2016) AS [Highest Schools], 
     dbo.fn_Function3(Code, 2016) AS [Average Students], 
     dbo.fn_Function4(Code, 2016) AS [Average Schools] 
    ) as calc 

但總的來說，@TimSchmelter是關於使用功能，如果避免完全正確有可能 - 標量函數通常對性能很差。在你的情況，你至少可以刪除fn_calculator功能：

select top (1000) 
    Region, 
    calc.[Highest Students], 
    calc.[Highest Schools], 
    calc.[Average Students], 
    calc.[Average Schools], 
    calc.[Highest Students] + calc.[Average Students] as [Total Students], 
    calc.[Highest Schools] + calc.[Average Schools] as [Total Schools] 
From myTable as t 
    outer apply (select 
     dbo.fn_Function1(Code, 2016) AS [Highest Students], 
     dbo.fn_Function2(Code, 2016) AS [Highest Schools], 
     dbo.fn_Function3(Code, 2016) AS [Average Students], 
     dbo.fn_Function4(Code, 2016) AS [Average Schools] 
    ) as calc 

你也可以使用一個CTE：

;with cte as (
    select top (1000) 
     t.Region, 
     dbo.fn_Function1(Code, 2016) AS [Highest Students], 
     dbo.fn_Function2(Code, 2016) AS [Highest Schools], 
     dbo.fn_Function3(Code, 2016) AS [Average Students], 
     dbo.fn_Function4(Code, 2016) AS [Average Schools] 
    From myTable as t 
) 
select 
    c.Region, 
    c.[Highest Students], 
    c.[Highest Schools], 
    c.[Average Students], 
    c.[Average Schools], 
    dbo.fn_Calculator(c.[Highest Students], c.[Average Students]) as [Total Students], 
    dbo.fn_Calculator(c.[Highest Schools], c.[Average Schools]) as [Total Schools] 
from cte as c