Recently I came across a requirement where I had to cleanse the data that I’m inserting in to MySQL database using regular expressions, so I started searching for a function to do this on MySQL, but unfortunately I couldn’t find any. There was one called UDB but that’s also you need to install a module and stuff like that. I gave up searching finally and wrote my own “regex_replace” MySQL function.
Below is the source code of my function;
DELIMITER $$ CREATE FUNCTION `regex_replace`(pattern VARCHAR(1000),replacement VARCHAR(1000),original VARCHAR(1000)) RETURNS VARCHAR(1000) DETERMINISTIC BEGIN DECLARE temp VARCHAR(1000); DECLARE ch VARCHAR(1); DECLARE i INT; SET i = 1; SET temp = ''; IF original REGEXP pattern THEN loop_label: LOOP IF i>CHAR_LENGTH(original) THEN LEAVE loop_label; END IF; SET ch = SUBSTRING(original,i,1); IF NOT ch REGEXP pattern THEN SET temp = CONCAT(temp,ch); ELSE SET temp = CONCAT(temp,replacement); END IF; SET i=i+1; END LOOP; ELSE SET temp = original; END IF; RETURN temp; END$$ DELIMITER ;
If you are using MySQL version 5.0.1 or higher, make sure you set the NO_BACKSLASH_ESCAPES mode ON, before you use the above function to replace any characters which are escaped with back slash “\”, ie: \A,\B,etc… See how to set the NO_BACKSLASH_ESCAPES mode here
Example on how to use this function
select regex_replace('[^a-zA-Z0-9\-]','','2my test3_text-to. check \\ my- sql (regular) ,expressions ._,');