Question

我知道MS T-SQL不支持正则表达式，但我需要类似的功能。这就是我想要做的事情：

我有一个varchar表字段，用于存储面包屑，如下所示：

/ ID1：组别/ ID2：类别2 / ID3：类别3 /

每个类别名称前面都有其类别ID，用冒号分隔。我想选择并显示这些面包屑，但我想删除类别ID和冒号，如下所示：

/组别/类别2 /类别3 /

之间的所有前导斜杠（/）以及冒号（:)都应该被删除。

我无法提取数据，在外部操作数据，然后重新插入表中;所以我试图在SELECT语句中完成这个。

由于SELECT中返回的行数，我也无法使用游标循环遍历每一行并使用嵌套循环清理每个字段。

可以这样做吗？

谢谢大家 - 杰伊

Answer 1

我认为最好的办法是使用递归的用户定义函数（UDF）。我在这里添加了一些代码，您可以使用它来传递字符串以获得您正在寻找的结果。

CREATE FUNCTION ufn_StripIDsFromBreadcrumb (@cIndex int, @breadcrumb varchar(max), @theString varchar(max))

RETURNS varchar(max)

AS

BEGIN
DECLARE @nextColon int
DECLARE @nextSlash int

SET @nextColon = CHARINDEX(':', @theString, @cIndex)
SET @nextSlash = CHARINDEX('/', @theString, @nextColon)
SET @breadcrumb = @breadcrumb + SUBSTRING(@theString, @nextColon + 1, @nextSlash - @nextColon)

IF @nextSlash != LEN(@theString)

     BEGIN
     exec @breadcrumb = ufn_StripIDsFromBreadcrumb @cIndex =  @nextSlash, @breadcrumb = @breadcrumb, @theString = @theString
     END
RETURN @breadcrumb
END

然后你可以用：

执行它

DECLARE @myString varchar(max)
EXEC @myString = ufn_StripIDsFromBreadcrumb 1, '/', '/ID1:Category1/ID2:Category2/ID3:Category3/'
PRINT @myString

Answer 2

这适用于SQL Server 2005及更高版本。

create table strings (
  string varchar(1000)
)

insert into strings values( '/ID1:Category1/ID2:Category2/ID3:Category3/' )  
insert into strings values( '/ID4:Category4/ID5:Category5/ID8:Category6/' )  
insert into strings values( '/ID7:Category7/ID8:Category8/ID9:Category9/' )  
go

with  
replace_with_wildcard ( restrung ) as 
( 
  select replace( string, '', '' ) 
  from strings

  union all 

  select  
    replace( restrung, substring( restrung, patindex( '%ID%', restrung ), 4 ), '' ) 
  from replace_with_wildcard 
  where patindex( '%ID%', restrung ) > 0 
) 

select restrung
from replace_with_wildcard 
where charindex( ':', restrung ) = 0
order by restrung

drop table strings

Answer 3

您可以使用分割功能执行此操作。以下拆分函数依赖于Numbers表的存在，该表实际上包含如下的数字顺序列表：

Create Table dbo.Numbers( Value int not null primary key clustered )
GO
With Nums As
    (
    Select ROW_NUMBER() OVER( Order By o.object_id ) As Num
    From sys.objects as o
        cross join sys.objects as o2
    )
Insert dbo.Numbers( Value )
Select Num
From Nums
Where Num Between 1 And 10000
GO  


Create Function [dbo].[udf_Split] (@DelimitedList nvarchar(max), @Delimiter nvarchar(2) = ',')
Returns @SplitResults TABLE (Position int NOT NULL PRIMARY KEY, Value nvarchar(max))
AS
/*
PURPOSE: to split the @DelimitedList based on the @Delimter
DESIGN NOTES:
    1. In general the contents of the next item is: NextDelimiterPosition - CurrentStartPosition
    2. CurrentStartPosition = 
        CharIndex(@Delimiter, A.list, N.Value)  = Current Delimiter position
        + Len(@Delimiter)                       + The number of delimiter characters 
        + 1                                     + 1 since the text of the item starts after the delimiter
    3. We need to calculate the delimiter length because the LEN function excludes trailing spaces. Thus
        if a delimiter of ", " (a comma followed by a space) is used, the LEN function will return 1.
    4. The DataLength function returns the number of bytes in the string. However, since we're using
        an nvarchar for the delimiter, the number of bytes will double the number of characters.
*/
Begin
    Declare @DelimiterLength int
    Set @DelimiterLength = DataLength(@Delimiter) / 2

    If Left(@DelimitedList, @DelimiterLength) <> @Delimiter
        Set @DelimitedList = @Delimiter + @DelimitedList

    If Right(@DelimitedList, @DelimiterLength) <> @Delimiter
        Set @DelimitedList = @DelimitedList + @Delimiter

    Insert @SplitResults(Position, Value)
    Select CharIndex(@Delimiter, A.list, N.Value) + @DelimiterLength            
        , Substring (
                    A.List
                    , CharIndex(@Delimiter, A.list, N.Value) + @DelimiterLength         
                    , CharIndex(@Delimiter, A.list, N.Value + 1)                            
                        - ( CharIndex(@Delimiter, A.list, N.Value) + @DelimiterLength ) 
                    )
    From dbo.Numbers As N
        Cross Join (Select @DelimitedList As list) As A
    Where N.Value > 0
        And N.Value < LEN(A.list)
        And Substring(A.list, N.Value, @DelimiterLength) = @Delimiter
    Order By N.Value

    Return
End

然后，您可能能够在删除前缀的情况下运行查询：

Select Table, Substring(S.Value, CharIndex(':', S.Value) + 1, Len(S.Value))
From Table
    Cross Apply dbo.udf_Split(Table.ListColumn, '/') As S

这将为您提供如下值：

Category1
Category2
Category3

然后，您可以使用FOR XML PATH再次合并它们：

Select Table.PK
    ,   Stuff(  (
                Select '/' + Substring(S.Value, CharIndex(':', S.Value) + 1, Len(S.Value))
                From Table As Table1
                    Cross Apply dbo.udf_Split(Table.ListColumn, '/') As S1
                Where Table1.PK = Table.PK
                Order By S1.Position
                For Xml Path('')
                ), 1, 1, '') As BreadCrumb
From Table

Answer 4

对于SQL Server 2005+，您可以通过以下方式获得正则表达式支持：

启用CLR（不需要重新启动实例）
上传您的CLR功能（在本例中为正则表达式替换）

使用本机TSQL，您需要为要删除的所有内容定义REPLACE语句：

SELECT REPLACE(
         REPLACE(
           REPLACE(''/ID1:Category1/ID2:Category2/ID3:Category3/'', 'ID1:', ''),
            'ID2:', ''), 
         'ID3:', '')

正则表达式或其他方面，您需要确保这些模式不会出现在实际数据中。

Answer 5

您可以使用SQL CLR。这是一个MSDN article：

Answer 6

declare @test1 nvarchar(max)
set @test1='/ID1:Category1/ID2:Category2/ID3:Category3/'
while(CHARINDEX('ID',@test1)<>0)
Begin
select @test1=REPLACE(@test1,SUBSTRING(@test1,CHARINDEX('ID',@test1),CHARINDEX(':',@test1)-
CHARINDEX('ID',@test1)+1),'') 
End
select @test1

在SQL中用通配符替换

6 个答案: