sql - 从sql中的字符串读取char，double，int模式

Question

你有一个像

set @string = 'ddd,1.5,1,eee,2.3,0,fff,1.2,ggg,6.123,1'

我想知道是否有办法提取字符串值并将它们放在第一行，double 值并将它们放在第二行和 int 值并将它们放在第三行。字符串逻辑就像这个

"string,double,int,string,double,int..."

但有些情况下

"string,double,int,string,double,string,double,int"

我希望在第三行中，默认情况下 int 应该是 1，这样表格就会看起来像这样。

First Row   Second Row  Third Row
ddd           1.5         1
eee           2.3         0
fff           1.2         1
ggg           6.123       1

我有一个代码，您可以在其中从字符串中提取所有值并将它们排成一行，但这还不够。

declare @string as nvarchar(MAX)

set @string = 'aaa,bbb,ccc,ddd,1.5,1,eee,2.3,1,fff,1.2,ggg,6.123,1'
;with tmp(DataItem, Data) 
as (
select LEFT(@string, CHARINDEX(',',@string+',')-1),
    STUFF(@string, 1, CHARINDEX(',',@string+','), '')
union all
select LEFT(Data, CHARINDEX(',',Data+',')-1),
    STUFF(Data, 1, CHARINDEX(',',Data+','), '')
from tmp
where Data > '')
select DataItem from tmp
option (maxrecursion 0)

Answer 1

最终版本(我希望):

由于 sql server 2008 在聚合函数的 over 子句中不支持 order by，我添加了另一个 cte 来添加行索引而不是 sum我在以前的版本中使用过:

;WITH cteAllRows as
(
     SELECT Item, 
            ItemIndex, 
            CASE WHEN ISNUMERIC(Item) = 0 THEN 'String'
            WHEN ISNUMERIC(Item) = 1 AND CHARINDEX('.', Item) > 0 THEN 'Double'
            WHEN ISNUMERIC(Item) = 1 AND CHARINDEX('.', Item) = 0 THEN 'Integer'
            END As DataType
     FROM dbo.SplitStrings_Numbers(@string, ',')
), cteAll as
(
    SELECT  Item, 
            DataType, 
            ItemIndex, 
            (
                SELECT COUNT(*)
                FROM cteAllRows tInner
                WHERE tInner.DataType = 'String'
                AND tInner.ItemIndex <= tOuter.ItemIndex
            ) As RowIndex
    FROM cteAllRows tOuter
)

其余的与以前的版本相同。

更新

我所做的第一件事是将字符串拆分函数更改为基于计数表的函数，以便我可以轻松地向其中添加行号。所以，如果您还没有理货表， create one .
如果您问自己什么是理货表以及为什么需要它， read this article by Jeff Moden :

SELECT TOP 10000 IDENTITY(int,1,1) AS Number
    INTO Tally
    FROM sys.objects s1       
    CROSS JOIN sys.objects s2 
ALTER TABLE Tally ADD CONSTRAINT PK_NumbersTest PRIMARY KEY CLUSTERED (Number)
GO

然后，根据计数表创建字符串拆分函数(取自 Aaron 的文章，但添加了行索引列):

CREATE FUNCTION dbo.SplitStrings_Numbers
(
   @List       NVARCHAR(MAX),
   @Delimiter  NVARCHAR(255)
)
RETURNS TABLE
WITH SCHEMABINDING
AS
   RETURN
   (
       SELECT   Item = SUBSTRING(@List, Number, CHARINDEX(@Delimiter, @List + @Delimiter, Number) - Number),
                ROW_NUMBER() OVER (ORDER BY Number) As ItemIndex
       FROM dbo.Tally
       WHERE Number <= CONVERT(INT, LEN(@List))
         AND SUBSTRING(@Delimiter + @List, Number, LEN(@Delimiter)) = @Delimiter
   );
GO

现在，我使用的技巧与前一个非常相似，只是现在我在第一个 cte 中添加了一个名为 RowIndex 的新列，这基本上是基于行的字符串计数的运行总和所有行的索引:

 SELECT Item, 
        CASE WHEN ISNUMERIC(Item) = 0 THEN 'String'
        WHEN ISNUMERIC(Item) = 1 AND CHARINDEX('.', Item) > 0 THEN 'Double'
        WHEN ISNUMERIC(Item) = 1 AND CHARINDEX('.', Item) = 0 THEN 'Integer'
        END As DataType,
        SUM(CASE WHEN ISNUMERIC(Item) = 0 THEN 1 END) OVER(ORDER BY ItemIndex) As RowIndex
 FROM dbo.SplitStrings_Numbers(@string, ',')

它给了我这个结果:

Item       DataType RowIndex
---------- -------- -----------
ddd        String   1
1.5        Double   1
1          Integer  1
eee        String   2
2.3        Double   2
0          Integer  2
fff        String   3
1.2        Double   3
ggg        String   4
6.123      Double   4
1          Integer  4

如您所见，我现在每行都有一个数字，所以从现在开始很简单:

;WITH cteAll as
(
     SELECT Item, 
            CASE WHEN ISNUMERIC(Item) = 0 THEN 'String'
            WHEN ISNUMERIC(Item) = 1 AND CHARINDEX('.', Item) > 0 THEN 'Double'
            WHEN ISNUMERIC(Item) = 1 AND CHARINDEX('.', Item) = 0 THEN 'Integer'
            END As DataType,
            SUM(CASE WHEN ISNUMERIC(Item) = 0 THEN 1 END) OVER(ORDER BY ItemIndex) As RowIndex
     FROM dbo.SplitStrings_Numbers(@string, ',')
), cteString AS
(
    SELECT Item, RowIndex
    FROM cteAll
    WHERE DataType = 'String'
), cteDouble AS
(
    SELECT Item, RowIndex
    FROM cteAll
    WHERE DataType = 'Double'
), cteInteger AS
(
    SELECT Item, RowIndex
    FROM cteAll
    WHERE DataType = 'Integer'
)

SELECT  T1.Item As [String],
        T2.Item As [Double],
        T3.Item As [Integer]
FROM dbo.Tally 
LEFT JOIN cteString T1 ON T1.RowIndex = Number 
LEFT JOIN cteDouble T2 ON t2.RowIndex = Number 
LEFT JOIN cteInteger T3 ON t3.RowIndex = Number
WHERE COALESCE(T1.Item, T2.Item, T3.Item) IS NOT NULL

这给了我这个结果:

String     Double     Integer
---------- ---------- ----------
ddd        1.5        1
eee        2.3        0
fff        1.2        NULL
ggg        6.123      1

如您所见，项目现在按字符串中的原始顺序排序。
感谢您的挑战，我已经有一段时间没有像样的挑战了:-)

第一次尝试

好吧，首先您必须将该字符串拆分为一个表。为此，您应该使用用户定义的函数。您可以从 Aaron Bertrand 的 Split strings the right way – or the next best way 中挑选最适合您的一款文章。

对于这个演示，我选择使用 SplitStrings_XML .

首先，创建函数:

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

现在，声明并初始化变量:

declare @string nvarchar(max) = 'ddd,1.5,1,eee,2.3,0,fff,1.2,ggg,6.123,1'

然后，创建 4 common table expressions - 一种用于所有项目，一种用于字符串，一种用于 double 型，一种用于整数。注意 row_number() 的使用函数 - 稍后将用于将所有结果连接在一起:

;WITH AllItems as
(
    SELECT Item, ROW_NUMBER() OVER(ORDER BY (select null)) as rn
    FROM dbo.SplitStrings_XML(@string, ',')
)

, Strings as
(
    SELECT Item as StringItem, ROW_NUMBER() OVER(ORDER BY (select null))  as rn
    FROM dbo.SplitStrings_XML(@string, ',')
    WHERE ISNUMERIC(Item) = 0
), Doubles as 
(
    SELECT Item as DoubleItem, 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 IntegerItem, ROW_NUMBER() OVER(ORDER BY (select null))  as rn
    FROM dbo.SplitStrings_XML(@string, ',')
    WHERE ISNUMERIC(Item) = 1 AND CHARINDEX('.', Item) = 0 
)

然后，从连接所有这些公用表表达式中进行选择。注意 COALESCE 的使用内置函数只返回至少存在一个值的行:

SELECT StringItem,  DoubleItem, IntegerItem
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(StringItem,  DoubleItem, IntegerItem) IS NOT NULL

结果:

StringItem  DoubleItem  IntegerItem
----------  ----------  -----------
ddd         1.5         1
eee         2.3         0
fff         1.2         1
ggg         6.123       NULL