Case-insensitive REPLACE in MySQL?

Alternative function for one spoken by fvox.

DELIMITER |
CREATE FUNCTION case_insensitive_replace ( REPLACE_WHERE text, REPLACE_THIS text, REPLACE_WITH text )
RETURNS text
DETERMINISTIC 
BEGIN
    DECLARE last_occurency int DEFAULT '1';

    IF LCASE(REPLACE_THIS) = LCASE(REPLACE_WITH) OR LENGTH(REPLACE_THIS) < 1 THEN
         RETURN REPLACE_WHERE;
    END IF;

    WHILE Locate( LCASE(REPLACE_THIS), LCASE(REPLACE_WHERE), last_occurency ) > 0  DO
      BEGIN
        SET last_occurency = Locate(LCASE(REPLACE_THIS), LCASE(REPLACE_WHERE));
         SET REPLACE_WHERE = Insert( REPLACE_WHERE, last_occurency, LENGTH(REPLACE_THIS), REPLACE_WITH);
         SET last_occurency = last_occurency + LENGTH(REPLACE_WITH);
      END;
    END WHILE;
    RETURN REPLACE_WHERE;
END;
|
DELIMITER ;

Small test:

SET @str = BINARY 'New York';
SELECT case_insensitive_replace(@str, 'y', 'K');

Answers: New Kork

If replace(lower()) doesn't work, you'll need to create another function.

My 2 cents.

Since many people have upgraded from MySQL to MariaDB those people will have available a new function called REGEXP_REPLACE. Use it as you would a normal replace, but the pattern is a regular expression.

This is a working example:

UPDATE `myTable`
SET `myField` = REGEXP_REPLACE(`myField`, '(?i)my insensitive string', 'new string') 
WHERE `myField` REGEXP '(?i)my insensitive string'

The option (?i) makes all the subsequent matches case insensitive (if put at the beginning of the pattern like I have then it all is insensitive).

See here for more information: https://mariadb.com/kb/en/mariadb/pcre/

Edit: as of MySQL 8.0 you can now use the regexp_replace function too, see documentation: https://dev.mysql.com/doc/refman/8.0/en/regexp.html

This modification of Luist's answer allows one to replace the needle with a differently cased version of the needle (two lines change).

DELIMITER |
CREATE FUNCTION case_insensitive_replace ( REPLACE_WHERE text, REPLACE_THIS text, REPLACE_WITH text )
RETURNS text
DETERMINISTIC 
BEGIN
  DECLARE last_occurency int DEFAULT '1';

  IF LENGTH(REPLACE_THIS) < 1 THEN
    RETURN REPLACE_WHERE;
  END IF;

  WHILE Locate( LCASE(REPLACE_THIS), LCASE(REPLACE_WHERE), last_occurency ) > 0  DO
    BEGIN
      SET last_occurency = Locate(LCASE(REPLACE_THIS), LCASE(REPLACE_WHERE), last_occurency);
      SET REPLACE_WHERE = Insert( REPLACE_WHERE, last_occurency, LENGTH(REPLACE_THIS), REPLACE_WITH);
       SET last_occurency = last_occurency + LENGTH(REPLACE_WITH);
    END;
  END WHILE;
  RETURN REPLACE_WHERE;
END;
|
DELIMITER ;