How to get all PDF links from HTML content using T-SQL - sql

Question

I am trying to retrieve all PDF links from a string column which contains HTML.
Example text of one column is:
<p>text here link
some other text home
link 2</p>
I need all links with .pdf extension.
I already tried function like this
ALTER function [dbo].[GetLinks] (#t nvarchar(max))
returns #Links table (link nvarchar(max))
as
begin
declare #strtpos int
set #strtpos=100
declare #endpos int
declare #lnk nvarchar(max)
while #strtpos > 6
begin
set #strtpos = PATINDEX('%href="%', #t)+6
if #strtpos>6 begin
--set #endpos = CHARINDEX ('"',#t,#strtpos+1)
set #endpos = PATINDEX('%.pdf"%',#t)+4
if #endpos>0 begin
set #lnk = substring(#t ,#strtpos, #endpos - #strtpos)
set #strtpos = PATINDEX('%href="%', #lnk)+6
set #t= RIGHT (#t, len(#t) - #endpos)
insert #Links values(#lnk)
end
end
end
return
end
And calling this function from SQL Server like this:
select top 1 * from dbo.GetLinks(' <p>text here link
some other text home
link 2</p>')
This returns the first link only when I match CHAR, but when I match string ".pdf" it returns long string. Please let me know if I am doing something wrong or need to change approach for this.

Answer 1

If your html column can be converted to XML like your example suggests, your can parse the href values in T-SQL using XML data type methods:
CREATE FUNCTION dbo.GetLinks (#t xml)
RETURNS #Links TABLE (link nvarchar(max))
AS
BEGIN
INSERT #Links
SELECT
AnchorTag.value('#href', 'nvarchar(MAX)') AS link
FROM #t.nodes('//a') AS AnchorTags(AnchorTag);
RETURN;
END;
GO
The same approach can be used with an inline TVF:
CREATE FUNCTION dbo.GetLinks (#t xml)
RETURNS TABLE
AS
RETURN (
SELECT
AnchorTag.value('#href', 'nvarchar(MAX)') AS link
FROM #t.nodes('//a') AS AnchorTags(AnchorTag)
);
GO

Answer 2

Xquery expression can do it simply
DECLARE #html xml = '<p>text here link<b v="3">ok</b>some other text home<a title="er">kj</a>link 2</p>'
select [pdfLink] = a.value('#href','varchar(max)')
from #html.nodes('//a[#href[contains(., ".pdf")]]') c(a)

Answer 3

If you are on SQL Server 2016+ you can use STRING_SPLIT.
DECLARE #string VARCHAR(8000) = '
<p>text here link
some other text home
link 2</p>';
SELECT TheUrl = split.value
FROM STRING_SPLIT(#string,'"') AS split
WHERE split.value LIKE '%.pdf';
Returns:
TheUrl
---------------------------
example.com/abc.pdf
www.example.com/abc123.pdf

Answer 4

If you can't convert your html into xml for whatever reason, you can still do this with regular string manipluation, though it is not pretty.
This solution (ironically) utilises an xml based string splitter to allow for multi-character delimiters, the output of which is then further filtered to only return the .pdf links:
create or alter function [dbo].[fn_StringSplitXML]
(
#str varchar(max) = '' -- String to split.
,#Delimiter varchar(10) = ',' -- Delimiting value to split on.
,#num int = null -- Which value to return.
)
returns table
as
return
select rn
,item
from(select rn = row_number() over(order by(select null))
,item = ltrim(rtrim(n.i.value('(./text())[1]','varchar(max)')))
from(select x = cast('<x>'+replace(#str,#Delimiter,'</x><x>')+'</x>' as xml).query('.')) as s
cross apply s.x.nodes('x') as n(i)
) as a
where rn = #num
or #num is null
;
declare #html varchar(1000) =
'<p>text here link
some other text home
link 2</p>
<input type="text" name="self closed tag" />
<b>some more text</b>
';
select left(s.item
,patindex('%.pdf%',s.item)+3
) as link
from dbo.fn_StringSplitXML(replace(replace(#html
,'>'
,''
)
,'<'
,''
)
,'href="'
,null
) as s
where patindex('%.pdf%',s.item) > 0;
Output
link
example.com/abc.pdf
www.example.com/abc123.pdf