MySQL: Why aren't url's matching when using REPLACE?

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My Situation:

I have url's in a field containing blog posts. The url's are being stored in my database with escape characters. My task at the moment is to replace some already inserted 'http' url's with 'https' url's, but REPLACE will match neither the original url nor the escaped url. I can't just replace every instance of 'http:', because I only want to affect certain links in each post, not every link.

I am very familiar with SQL, as well as REPLACE, so I'm not just asking how REPLACE works and how to use it. Another user here has tested my queries in his environment and they work. So, there must be something in my configuration that is preventing the queries from functioning as expected.

I have searched this site and google extensively for several hours and have found nothing specifically addressing my issue. Everything I have tried is included below and if there is something else I should try, I don't know what that is and I haven't found any suggestions/posts/comments that suggest doing anything differently.

Example URL:

As Stored in DB:


Code to Re-Create Situation:

    post_content longtext NOT NULL,
    PRIMARY KEY (id)

        ('content content content <a href="http:\\/\\/">Link I want to change</a> content content content <a href="http:\\/\\/">Link I don\'t want to change</a> content content content <a href="http:\\/\\/">Link I want to change</a> content content content <a href="http:\\/\\/">Link I don\'t want to change</a>');

If I run

    post_content = REPLACE(post_content, '', '');


    post_content = REPLACE(post_content, 'http:\/\/', '');

zero records are affected.

For testing purposes, I ran the following query which returns 0 rows.

    post_content LIKE '%'
    post_content LIKE '%http:\/\/'
    post_content LIKE '%http:\\/\\/'
    post_content LIKE 'http:%/%/';

If I run:

    post_content LIKE '%http:_/_/'

It does return matches, but that doesn't solve the real problem of how to match when using UPDATE/REPLACE.

I have tried on two different servers and I get the same results on both.

I have tried the following Engine/Collation combinations and all return the same 0 records results:





Anybody know how I can write these queries so that REPLACE will find matches to those url's or what settings in my database or PhpMyAdmin may be causing the queries to return/affect 0 rows?

I think the backslash must be escaped in MySQL

field_name LIKE 'http:\\/\\/'

Of course one could go for sure and use the single char wildcard __

field_name LIKE 'http:_/_/'

or for your both cases: an optional backslash:

field_name LIKE 'http:%/%/'

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I'm still baffled as to why the queries with LIKE won't work, but, sadly, using those to narrow down the problem clouded my judgement and I didn't try all the same combinations in the REPLACE functions.

The following works:

    post_content = REPLACE(post_content, 'http:\\/\\/', '');

If anyone can explain to me why these combinations work with REPLACE, but not with LIKE, I'd really love to know. Thanks!

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There is no reason, your query won't work if you have run properly, there is something else, you may be missing here.

UPDATE test1 SET name_1 = REPLACE(name_1, 'http:\/\/', '')

works well and does the job of repalcing the \/ with /. See screen-shot attached,

You may have some other problem, please check and update the question, if so.

Edit after comments

If you have more data points in URL, change query like below.

UPDATE test1 SET name_1 = REPLACE(name_1, '\/', '/')

Above will replace all the occurrence of \/ with /.

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As \\ did not work to represent/escape a backslash, use regular expression functions:

REGEXP_REPLACE(field, 'http:\\/\\/', 'http://')

Here \\ should work.

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  • Fundamental question here should be: what for you store escaped data in your database?!
  • The fundamental question is as I asked it. I don't have any control over the program that is doing the inserts. My job is to deal with the data once it gets there.
  • I spoke too soon in my first comment, so I deleted it. Your second option does match when using SELECT/LIKE. However, it does not work when using UPDATE/REPLACE. Neither your first, nor third option works in either case. Thanks, though!
  • Thanks, but you haven't answered my question. My query is exactly the same as yours, other than you've used test1 and name_1 instead of table and field. So, if you have some suggestion as to why your version of that query is working and mine isn't, I'd appreciate more info.
  • Do run following query and see , how many records get selected. I feel you may not full long URL in database. ` select * from test1 where name_1,='http:\/\/'` , I feel it will return 0. I assumed you are running query on terminal.
  • I'm running the queries exactly as written above (with the actual field and table names) in PhpMyAdmin and the results are always zero. I cannot use "where name_1 = 'http:\/\/' because the field contains complete blog posts, not just the urls.
  • Perfect, now, you hit the actual problem, so you have to change your query, I'll update the answer, based on this comment, I believe it will work for you.
  • That, too, affects zero rows. I tested it on one record, but, even if it had worked, it would be very risky for me to run that query against all the records. There could be legit instance of '\/' in the data. If you're able to affect results, I guess that at least means it's not the queries themselves and must be something in the environment or configuration. ... Sorry if I sounded rude in my first response to you. I've got a migraine and didn't articulate well. I appreciate your efforts!
  • Thanks, but neither worked for me. I get a function does not exist error using REGEXP_LIKE. The REGEXP_REPLACE causes no errors, but affects 0 rows. But, I'd read that neither function worked in standard MySQL, only MariaDB, so, at least now I know that REGEXP_REPLACE does work. I did figure out my answer, but I appreciate your input. Thanks!