MySQL Bugs: #113153: Documentation on how to use captured groups in REGEXP

Bug #113153	Documentation on how to use captured groups in REGEXP_REPLACE
Submitted:	20 Nov 2023 20:46	Modified:	21 Nov 2023 6:46
Reporter:	Nuno P	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S3 (Non-critical)
Version:	8.0	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
Following a recent migration from MariaDB to MySQL, I was wondering why my "REGEXP_REPLACE" expressions were not correctly replacing when using captured groups.

Apparently, while MariaDB uses "\\1" format, MySQL uses "$1".

I was trying to see what the documentation says, but seems that there are no examples at all on how to use groups, in the page:

https://dev.mysql.com/doc/refman/8.0/en/regexp.html#function_regexp-replace

How to repeat:
MariaDB:

REGEXP_REPLACE(column, '.*(xx).*', '\\1')

MySQL:

REGEXP_REPLACE(column, '.*(xx).*', '$1')

Suggested fix:
My suggestion is that the documentation is improved to give at least one example on how to use captured groups in REGEXP_REPLACE.

Example for MariaDB:
https://mariadb.com/kb/en/regexp_replace/

Hello Nuno P,

Thank you for the document enhancement request.

regards,
Umesh

Absolutely. I just ran into this and couldn't find the $1 documented anywhere; in the end, I had to talk with another SQL architect who just "knew" the answer.