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Simulating regex capture groups in mysql
Good day,
I have many rows of data stored in a MySQL table. A typical value could look something like this:
::image-gallery::
::gallery-entry::images/01.jpg::/gallery-entry::
::/image-gallery::
Is there a way - by means of a regular expression that I can a) extract the term image gallery from the first line (it could be any phrase, not just image-gallery) and then extract the center line as two separate values like this:
gallery-entry and then images/01.jpg
There could be many lines of ::gallery-entry:: values, and they could be called anything as well. A more complete example would be:
::image-gallery::
::title::MY GALLERY::/title::
::date::2011-05-20::/date::
::gallery-entry::images/01.jpg::/gallery-entry::
::/image-gallery::
In essence I want this information: The content type (image-gallery) in the above case, first line and last line. Then I need the title as a key value style pair, so title as the key and MY GALLERY as the value. Then, subsequently, I would need all the rows of fields thereafter (gallery-entry) as key value pairs too.
This is for a migration script where data from an old system will be migrated over to a new system with different syntax.
If MySQL select statements would not work, would it be easier to parse the results with a PHP script for data extraction?
Any and all help is always appreciated.
Kind regards,
Simon
Try this regex:
::image-gallery::\s+::title::(.*?)::/title::.*?::gallery-entry::(.*?)::/gallery-entry::\s+::/image-gallery::
Use single-line mode (/pattern/s) so the .*? chews up newlines.
Your key-value pairs will be:
title: $1 (matching group 1)
gallery-entry: $2 (matching group 2)
From simulating-regex-capture-groups-in-mysql there does not seem to be a way to easily capture groups with a regex in mysql. The reason is that MySQL does not natively support capture groups in a regex. If you want that functionality you can use a server side extension like lib_mysqludf_preg to add that capability to MySQL.
The easiest way is to extract the whole column with SQL and then do the text matching in another language (such as php).
In my tests kenbritton's regex didn't work, but building off of it the following regex worked on your test data:
::image-gallery::\s+::title::(.*?)::\/title::\s+(?:.*\s+)*::gallery-entry::(.*?)::\/gallery-entry::\s+::\/image-gallery::
Related
I have an JSON string stored in the database and I need to SQL COUNT based on the WHERE condition that is in the JSON string. I need it to work on the MYSQL 5.5.
The only solution that I found and could work is to use the REGEXP function in the SQL query.
Here is my JSON string stored in the custom_data column:
{"language_display":["1","2","3"],"quantity":1500,"meta_display:":["1","2","3"]}
https://regex101.com/r/G8gfzj/1
I now need to create a SQL sentence:
SELECT COUNT(..) WHERE custom_data REGEXP '[HELP_HERE]'
The condition that I look for is that the language_display has to be either 1, 2 or 3... or whatever value I will define when I create the SQL sentence.
So far I came here with the REGEX expression, but it does not work:
(?:\"language_display\":\[(?:"1")\])
Where 1 is replaced with the value that I look for. I could in general look also for "1" (with quotes), but it will also be found in the meta_display array, that will have different values.
I am not good with REGEX! Any suggestions?
I used the following regex to get matches on your test string
\"language_display\":\[(:?\"[0-9]\"\,)*?\"3\"(:?\,\"[0-9]\")*?\]
https://regex101.com/ is a free online regex tester, it seems to work great. Start small and work big.
Sorry it doesn't work for you. It must be failing on the non greedy '*?' perhaps try without the '?'
Have a look at how to serialize this data, with an eye to serializing the language display fields.
How to store a list in a column of a database table
Even if you were to get your idea working it will be slow as fvck. Better off to process through each row once and generate something more easily searched via sql. Even a field containing the comma separated list would be better.
not sure how far I'm going to get with this, but I'm going through a database removing certain bits and pieces in preparation for a conversion to different software.
I'm struggling with the image tags as on the site they currently look like
[img:<string>]<image url>[/img:<string>]
those strings are in another field called bbcode_uid
The query I'm running to make the changes so far is
UPDATE phpbb_posts SET post_text = REPLACE(post_text, '[img:]', '');
So my actual question, is there any way of pulling in each string from bbcode_uid inside of that SQL query so that I don't have to run the same command 10,000+ times, changing the unique string every time.
Alternatively could I include something inside [img:] to also include the next 8 characters, whatever they may be, as that is the length of the string that is used.
Hoping to save time with this, otherwise I might have to think of another way of doing it.
As requested.
The text I wish to replace would be
[img:1nynnywx]http://i.imgur.com/Tgfrd3x.jpg[/img:1nynnywx]
I want to end up with just
http://i.imgur.com/Tgfrd3x.jpg
Just removing the code around the URL, however each post_text has a different string which is contained inside bbcode_uid.
Method 1
LIB_MYSQLUDF_PREG
If you want more regular expression power in your database, you can consider using LIB_MYSQLUDF_PREG. This is an open source library of MySQL user functions that imports the PCRE library. LIB_MYSQLUDF_PREG is delivered in source code form only. To use it, you'll need to be able to compile it and install it into your MySQL server. Installing this library does not change MySQL's built-in regex support in any way. It merely makes the following additional functions available:
PREG_CAPTURE extracts a regex match from a string. PREG_POSITION returns the position at which a regular expression matches a string. PREG_REPLACE performs a search-and-replace on a string. PREG_RLIKE tests whether a regex matches a string.
All these functions take a regular expression as their first parameter. This regular expression must be formatted like a Perl regular expression operator. E.g. to test if regex matches the subject case insensitively, you'd use the MySQL code PREG_RLIKE('/regex/i', subject). This is similar to PHP's preg functions, which also require the extra // delimiters for regular expressions inside the PHP string
you can refer this link :github.com/hholzgra/mysql-udf-regexp
Method 2
Use php program, fetch records one by one , use php preg_replace
refer : www.php.net/preg_replace
reference:http://www.online-ebooks.info/article/MySql_Regular_Expression_Replace.html
You might be able to do this with substring_index().
The following will work on your example:
select substring_index(substring_index(post_text, '[/img:', 1), ']', -1)
I don't know if there is a better description of my problem, but here is what I need help with:
I have a field with lots of data, and the part I need to solve looks like this:
::field_x::<br />||field_x||519||/field_x||<br />||field_x||281||/field_x||<br />::/field_x::
I have to extract each number (id) from this, 519 and 281 in this example, and insert them in a field in another table, separated by spaces or commas. I know how to use SUBSTRING - LOCATE method, but that would return only the first instance, so is there a method to extract them all in one go?
SUBSTRING INDEX LOCATE will work. There is no built in functionality for regular expressions so unless you handle it before it gets to mysql...you're stuck using the SUBSTRING INDEX LOCATE method...
If you need to iterate through a dataset, you will need to initiate a cursor, or FOR loop and use a stored proc.
parse results in MySQL via REGEX
I have a list of a million or urls in an mysql table.
I need to cleanse the data (extract domains) so I can be confident about DISTINCT type queries.
Data is in several different types: -
www.domain.tld
domain.tld
http://domain.tld
https://vhost.domain.tld
domain.tld/
There are invalid domains and empty data.
Ideally I'd like to do something along the lines of : -
UPDATE table1 SET domain = website REGEXP '^(https?://)?[a-zA-Z0-9\\\\.\\\\-]+(/|$|\\\\?)'
domain being a new empty field, website being the original url.
You can't use regex like that in MySQL as is, but apparently you can some some UDFs that implement it. See:
How to do a regular expression replace in MySQL?
https://launchpad.net/mysql-udf-regexp
http://www.mysqludf.org/lib_mysqludf_preg/
In field post_content I have a string like this in nearly 800 rows:
http://somesite.com/">This is some site</a>
I need to remove everything from "> onwards so that it leaves just the URL. I can't do a straight find and replace because the text is unique.
Any clues? This is really my first foray into MySQL database modifications but I did do an extensive search before posting here.
Thanks,
~Kyle~
From this site: http://www.regular-expressions.info/mysql.html
LIB_MYSQLUDF_PREG
If you want more regular expression power in your database, you can consider using LIB_MYSQLUDF_PREG. This is an open source library of MySQL user functions that imports the PCRE library. LIB_MYSQLUDF_PREG is delivered in source code form only. To use it, you'll need to be able to compile it and install it into your MySQL server. Installing this library does not change MySQL's built-in regex support in any way. It merely makes the following additional functions available:
Here it comes...
PREG_CAPTURE extracts a regex match from a string. PREG_POSITION returns the position at which a regular expression matches a string. PREG_REPLACE performs a search-and-replace on a string. PREG_RLIKE tests whether a regex matches a string.
Sounds exactly what you're looking for.
All these functions take a regular expression as their first parameter. This regular expression must be formatted like a Perl regular expression operator. E.g. to test if regex matches the subject case insensitively, you'd use the MySQL code PREG_RLIKE('/regex/i', subject). This is similar to PHP's preg functions, which also require the extra // delimiters for regular expressions inside the PHP string.
See this post: How to do a regular expression replace in MySQL?
Either that or you could just write a script in any lanugage which goes through each record, does a regex replacement and then updates the field. For more info on regex, see here: http://www.regular-expressions.info/reference.html
There's a number of options. One might be to use SUBSTRING_INDEX():
UPDATE
table
SET field = SUBSTRING_INDEX( field, '">', 1 )
It's possible - there is a syntax for User Defined Functions which would let you pass in a regular expression pattern that matches the link and strips everything else.
However, this is quite complicated for somebody new to MySQL, and from your question, this sounds like a one-off. In which case - why not just use Excel and then reimport the data?
Great stuff!
All seems doable with a little bit of time and self education.
In the end, I exported that table as a CSV in Sequel Pro and did some nifty find and replace work in Coda. Not as sophisticated as your suggestions, but it worked.
Thanks again,
~Kyle~