It has been deprecated because there are better alternatives:
* In PHP: using the PCRE functions and the /i flag for case-insensitivity.
* In SQL: depends on the DBMS but many problems can be solved by using the right charset and collation. In MySQL you'd use, for example, utf8_general_ci on the column. [1]

[1] http://dev.mysql.com/doc/refman/5.6/en/charset-general.html

Hi. There is just one use case in which nor PCRE nor charset and collation are useful. This case is solvable with sql_regcase.

Please consider this use case:
"perform a case insensitive and accent insensitive word search (must match only entire words)"

- utf8_general_ci allows you to make an equality (WHERE field = value) case and accent insensitive search but it doesn't allow you to specify an entire word match (word boundaries markers not recognized)
- LIKE allows you case and accent insensitive search but you have to manually specify all combinations of possible word boundaries charactes (word boundaries markers not recognized)
- word boundaries [[:<:]] and [[:>:]] are supported in REGEXP, who is a single byte functions so don't perform accent insensitive search.

The solution is to use REGEXP with word boundaries and the word modified in the way sql_regcase does.

Used on http://www.genovaperte.it

sql_regcase() has a very limited usage as far as I can see: matching single-byte characters when you need a REGEXP in MySQL. Because (1) it won't work correctly with multibyte characters, especially with more than one, (2) LIKE handles the general don't-need-full-regular-expressions use case, and (3) like I said before the PCRE functions are better for use in just PHP.

If you really need the functionality then there is a straightforward userland solution: the one started by @irker on the manual page. Could use some touching up though, like using "(up|low)" instead of the flawed "[uplow]". (Searching around for "mb_sql_regcase" seems to turn up a number of results.)