如何在sql中索引我的行？

Question

我有以下功能：

CREATE FUNCTION dbo.SplitStrings_XML 
(
    @List  NVARCHAR(MAX), 
    @Delimiter NVARCHAR(255) 
) 
RETURNS TABLE 
WITH SCHEMABINDING 
AS 
    RETURN 
    ( 
     SELECT Item = y.i.value('(./text())[1]', 'nvarchar(4000)') 
     FROM 
     ( 
     SELECT x = CONVERT(XML, '<i>' 
      + REPLACE(@List, @Delimiter, '</i><i>') 
      + '</i>').query('.') 
    ) AS a CROSS APPLY x.nodes('i') AS y(i) 
    ); 
GO 

和下面的代碼：

declare @string nvarchar(max) = 'aaa,1.3,1,bbb,1.5,ccc,2.0,1' 
;WITH AllItems as 
(
    SELECT Item, ROW_NUMBER() OVER(ORDER BY (select null)) as rn 
    FROM dbo.SplitStrings_XML(@string, ',') 
) 
, Strings as 
(
    SELECT Item as Name, ROW_NUMBER() OVER(ORDER BY (select null)) as rn 
    FROM dbo.SplitStrings_XML(@string, ',') 
    WHERE ISNUMERIC(Item) = 0 
), Doubles as 
( 
    SELECT Item as Measure, ROW_NUMBER() OVER(ORDER BY (select null)) as rn 
    FROM dbo.SplitStrings_XML(@string, ',') 
    WHERE ISNUMERIC(Item) = 1 AND CHARINDEX('.', Item) > 0 
), Integers as 
(
    SELECT Item as Value, ROW_NUMBER() OVER(ORDER BY (select null)) as rn 
    FROM dbo.SplitStrings_XML(@string, ',') 
    WHERE ISNUMERIC(Item) = 1 AND CHARINDEX('.', Item) = 0 
) 

SELECT Name, Measure, Value 
FROM AllItems A 
LEFT JOIN Strings S ON A.rn = S.rn 
LEFT JOIN Doubles D ON A.rn = D.rn 
LEFT JOIN Integers I ON A.rn = I.rn 
WHERE COALESCE(Name, Measure, Value) IS NOT NULL 

在這段代碼中，我們得到了一個@string = 'aaa,1.3,1,bbb,1.5,ccc,2.0,1'，返回字符在名爲Name行，在返回的雙重價值行命名Measure並在名爲Value行中的int值，問題是，在我的字符串我一直一個Name and Measure但有時Value失蹤，我想向一個NULL值在該空間。所以在我的例子

我shouldhave像

Name  Measure Value 
---------+--------+------- 
aaa  1.3  1 
bbb  1.5  NULL 
ccc  2.0  1 

相反，我有：

Name  Measure Value 
---------+--------+------- 
aaa  1.3  1 
bbb  1.5  1 
ccc  2.0  NULL 

Answer 1

首先，我建議您修改返回的項目數的函數。但是，這不是必要的，因爲你的row_number()這樣做。

然後，我假設「缺失值」的意思是「,,」。

如果是的話，我會建議定義的CTE爲：

WITH AllItems as (
     SELECT Item, ROW_NUMBER() OVER (ORDER BY (select null)) as rn 
     FROM dbo.SplitStrings_XML(@string, ',') 
    ), 
    Strings as (
     SELECT Item as Name, ROW_NUMBER() OVER (ORDER BY (select null)) as rn 
     FROM AllItems ai 
     WHERE ai.rn % 3 = 1 
    ), 
    Doubles as ( 
     SELECT Item as Measure, ROW_NUMBER() OVER (ORDER BY (select null)) as rn 
     FROM AllItems ai 
     WHERE ai.rn % 3 = 2 
    ), 
    Integers as (
     SELECT Item as Value, ROW_NUMBER() OVER(ORDER BY (select null)) as rn 
     FROM AllItems ai 
     WHERE ai.rn % 3 = 0 
    ) 
. . .