Case-insensitive REPLACE in MySQL?

Question

MySQL runs pretty much all string comparisons under the default collation... except the REPLACE command. I have a case-insensitive collation and need to run a

Answer 1

In case of 'special' characters there is unexpected behaviour:

SELECT case_insensitive_replace('A', 'Ã', 'a')

Gives

a

Which is unexpected... since we only want to replace the à not A

What is even more weird:

SELECT LOCATE('Ã', 'A');

gives

0

Which is the correct result... seems to have to do with encoding of the parameters of the stored procedure...

Answer 2

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 ;