Extract substring from string in SQL
I need to extract a text that is surrounded by ***[some te开发者_运维百科xt]
strings, like in the following example:
some text
some text
***[some text]
THIS SHOULD BE EXTRACTED
***[some text]
some text
some text
some text
some text
some text
***[some text]
THIS SHOULD BE EXTRACTED TOO
***[some text]
some text
the output should be:
THIS SHOULD BE EXTRACTED
THIS SHOULD BE EXTRACTED TOO
I tried PATINDEX
like here, but couln't find the way to extract the string.
PATINDEX('%[*][*][*][[]%]%%[*][*][*][[]%]%',@Text)
I am looking forward to hearing any suggestions.
For the somewhat easier case raised in the comments you could do
;WITH T(C) AS
(
SELECT '
some text
some text
***[some text 1]
THIS SHOULD BE EXTRACTED
***[some text 2]
some text
some text
some text
some text
some text
***[some text 1]
THIS SHOULD BE EXTRACTED TOO
***[some text 2]
some text'
)
SELECT col.value('.','varchar(max)')
FROM T
CROSS APPLY (SELECT CAST('<a keep="false">' +
REPLACE(
REPLACE(C,'***[some text 2]','</a><a keep="false">'),
'***[some text 1]','</a><a keep="true">') +
'</a>' AS xml) as xcol) x
CROSS APPLY xcol.nodes('/a[@keep="true"]') tab(col)
Not a regex solution and I'm still a SQL novice so may not be optimal but you should be able to parse with a WHILE
loop using
CHARINDEX
for the ***
then using that as a starting point to
CHARINDEX
to the LF
Use that as the starting point for a
SUBSTRING
with the ending point being a CHARINDEX
of the next ***
concatenate the Substring to your output, move past the ending ***
and loop to find the next one.
I'll play with it some and see if I can add an example.
EDIT - This probably needs more error checking
declare @inText nvarchar(2000) = 'some text
some text
***[some text]
THIS SHOULD BE EXTRACTED
***[some text]
some text
some text
some text
some text
some text
***[some text]
THIS SHOULD BE EXTRACTED TOO
***[some text]
some text '
declare @delim1 nvarchar(50) = '***'
declare @delim2 char = char(10)
declare @output nvarchar(1000) = ''
declare @position int
declare @positionEnd int
set @position = CHARINDEX(@delim1,@inText)
while (@position != 0 and @position is not null)
BEGIN
set @position = CHARINDEX(@delim2,@inText,@position)
set @positionEnd = CHARINDEX(@delim1,@inText,@position)
set @output = @output + SUBSTRING(@inText,@position,@positionEnd-@position)
set @position = CHARINDEX(@delim1,@inText,@positionEnd+LEN(@delim1))
END
select @output
You can find this in my blog: http://sql-tricks.blogspot.com/2011/04/extract-strings-with-delimiters.html It is pure solution with no additional modification, only delimiters sequences should be decalred.
I may be wrong but I don't think there's a clean way to do this directly in SQL. I would use a CLR stored procedure and use regular expressions from C# or your .NET language of choice.
See this article (or this article) for a relevant example using regexes.
I believe you can use the xp_regex_match as described in http://www.codeproject.com/KB/mcpp/xpregex.aspx?q=use+sql+function+to+parse+text to parse your nvarchar field. I wrote something similar quite a while back.
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