Remove sub-string from data in sql table column - sql

Question

I have a table that has a bunch of url's within a certain column. We no longer want a certain url within the table and instead of manually updating each data record I was curious if there is a way to remove just a certain type of url through an update query?
For instance, a data record with the following url's exists:
Presentation (PowerPoint File)<br> Presentation (Webcast)
and I want to remove the smil url so the data only shows:
Presentation (PowerPoint File)<br>
I want to remove the entire "smil" url from this string (from ), and every other smil url from the other records (the other records are similar with a different smil file name). Some of the records could have more than two urls, BUT the "smil" url is always the last one.

Answer 1

Preserving some of the comment history so future readers understand the decision points before implementing the solution
Does it always follow the pattern of text<br>text
there are a few times where there are two urls and they exclude the <br> and then there are a few times where it is just the smil url within the data.
You haven't clearly define what a "smil" url is. Is it one with smil in it anywhere? With the file suffix being .smil? With /smil/ in the path? some combination of these?
The problem you're going to have is that to properly solve this, you'll need to be able to have some insight into the html fragments. That's usually a .NET thing, the string matching in TSQL is likely to be insufficient for your needs. You could try taking multiple passes as it. If it follows the text<br>text pattern, you could left(myCol, charindex(mycol, '<br>')) where Mycol like '%smil%' and keep taking passes at it until you've found all the patterns.
#billinkc: I see where you are going, I was thinking if it would be possible to remove everything from the start of <a href="xxx since those "smil" links all start with that character string.
And there'd never be the case of streaming<br>foo? If so, then yeah, search for the <a href="http: using charindex/patindex (can never remember which) and then slice it out with left/substring.
#billinkc: yup that will always be the case. the "streaming" url is ALWAYS last. Ok this was easier than I thought, just needed some outside eyes. Thank you.
Given that we know we don't have to worry about anything useful existing after the smil url and that the url will always be an external, we can safely use a left/substring approach like
DECLARE #Source table
(
SourceUrl varchar(200)
)
INSERT INTO #Source
(SourceUrl)
VALUES
('Presentation (PowerPoint File)<br> Presentation (Webcast)');
-- INSPECT THIS, IF APPROPRIATE THEN
SELECT
S.SourceUrl AS Before
, CHARINDEX('<a href="http://', S.SourceUrl) AS WhereFound
, LEFT(S.SourceUrl, CHARINDEX('<a href="http://', S.SourceUrl) -1) AS After
FROM
#Source AS S
WHERE
S.SourceUrl LIKE '%smil%';
-- Only run this if you like the results of the above
UPDATE
S
SET
SourceUrl = LEFT(S.SourceUrl, CHARINDEX('<a href="http://', S.SourceUrl) -1)
FROM
#Source AS S
WHERE
S.SourceUrl LIKE '%smil%';