字符串替换字符串的特定部分 [英] String replace specific part of string

问题描述

我有这样的文字

Key:Value
Key2:Value2
Key3:Value3

i have
a very 
long
uncommom
text which i need to drop

Key4:Valu4

第二个例子是

Key:Value
Key2:Value2
Key3:Value3
i have a very long uncommom text which i need to drop

Key4:Valu4

重点是去掉句子

i have a very long uncommom text which i need to drop

来自这两个 SQL 字符串.我需要提到在包含 CHAR(10) 和 CHAR(13) 里面.

from those two SQL strings. I need to mention in contains CHAR(10) and CHAR(13) inside.

我需要在键值对上保留新行.

I need to keep new lines on key:value pairs.

如何实现这一目标?

这行不通.

Replace(@string,'i have a very long uncommom text which i need to drop
','')

还有什么办法可以用一个替换双/三/四新换行符?

Also is there any way to replace double/triple/quadruple new line breaks with just one?

推荐答案

以下代码演示了一种将字符串拆分为单独行并重新组合包含冒号的行的方法.它保持输入行的顺序并且不需要任何最近的功能，例如 String_Split.

The following code demonstrates one way of splitting the string into separate lines and reassembling the lines that contain a colon. It maintains the order of the input lines and does not require any recent features, e.g String_Split.

-- Sample data.
declare @Newline as VarChar(2) = Char(10) + Char(13);
declare @Sample as VarChar(1024) =
  'Key:Value' + @Newline +
  'Key2:Value2' + @Newline +
  'Key3:Value3' + @Newline +
  @Newline +
  'i have' + @Newline +
  'a very ' + @Newline +
  'long ' + @Newline +
  'uncommom' + @Newline +
  'text which i need to drop' + @Newline +
  @Newline +
  'Key4:Valu4';

-- Display the sample data.
select @Sample as Sample, Replace( @Sample, @Newline, '¶' ) as VisibleSample;

-- Test the splitter.
select ItemNumber, Item, Replace( Item, @Newline, '¶' ) as VisibleItem
  from dbo.DelimitedSplit8K( @Sample, @Newline )
  where Item like '%:%';

-- Reassemble the items that include a colon.
declare @Result as NVarChar(1024) = Stuff(
  ( select @Newline + Item
      from dbo.DelimitedSplit8K( @Sample, @Newline )
      where Item like '%:%'
      order by ItemNumber for XML path(''), type).value('.[1]', 'VarChar(max)' ),
    1, Len( @NewLine ), '' );
select @Result as Result, Replace( @Result, @Newline, '¶' ) as VisibleResult;

拆分器是Jeff Moden's 处理可变长度分隔符的代码:

The splitter is a modified version of Jeff Moden's code which handles a variable length delimiter:

CREATE FUNCTION [dbo].[DelimitedSplit8K]
--===== Define I/O parameters
        (@pString VARCHAR(8000), @pDelimiter VARCHAR(16))
--WARNING!!! DO NOT USE MAX DATA-TYPES HERE!  IT WILL KILL PERFORMANCE!
RETURNS TABLE WITH SCHEMABINDING AS
 RETURN
--===== "Inline" CTE Driven "Tally Table" produces values from 1 up to 10,000...
     -- enough to cover VARCHAR(8000)
  WITH E1(N) AS (
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
                ),                          --10E+1 or 10 rows
       E2(N) AS (SELECT 1 FROM E1 a, E1 b), --10E+2 or 100 rows
       E4(N) AS (SELECT 1 FROM E2 a, E2 b), --10E+4 or 10,000 rows max
 cteTally(N) AS (--==== This provides the "base" CTE and limits the number of rows right up front
                     -- for both a performance gain and prevention of accidental "overruns"
                 SELECT TOP (ISNULL(DATALENGTH(@pString),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4
                ),
cteStart(N1) AS (--==== This returns N+1 (starting position of each "element" just once for each delimiter)
                 SELECT 1 UNION ALL
                 SELECT t.N+ Len( @pDelimiter ) FROM cteTally t WHERE SUBSTRING(@pString,t.N, Len( @pDelimiter ) ) = @pDelimiter
                ),
cteLen(N1,L1) AS(--==== Return start and length (for use in substring)
                 SELECT s.N1,
                        ISNULL(NULLIF(CHARINDEX(@pDelimiter,@pString,s.N1),0)-s.N1 ,8000)
                   FROM cteStart s
                )
--===== Do the actual split. The ISNULL/NULLIF combo handles the length for the final element when no delimiter is found.
 SELECT ItemNumber = ROW_NUMBER() OVER(ORDER BY l.N1),
        Item       = SUBSTRING(@pString, l.N1, l.L1)
   FROM cteLen l
;

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