MySQL SELECT pattern replace with results from another table - mysql

Question

How do I substitute values in a SELECT with text matches to rows in another table?
**products**
> +-------+--------------------------------------------------+
> | id | description |
> +-------+--------------------------------------------------+
> | 10001 | This product is %block1% and %block4% |
> | 10002 | This product is %block2%, %block3%, and is %block4% |
> +-------+--------------------------------------------------+
**descriptions**
> +-----------+-------------------+
> | blockname | blockcontent |
> +-----------+-------------------+
> | %block1% | 5 feet tall |
> | %block2% | matte white |
> | %block3% | makes music |
> | %block4% | made of real wood |
> +-----------+-------------------+
Ideally, I'd like to run a single query that returns
> +-------+--------------------------------------------------+
> | id | newdescription |
> +-------+--------------------------------------------------+
> | 10001 | This product is 5 feet tall and made of real wood |
> | 10002 | This product is matte white, makes music, and is made of real wood |
> +-------+--------------------------------------------------+
I've investigated REPLACE() and SUBSTITUTE() but they don't appear to be what I am looking for.

Answer 1

You can create function:
DROP FUNCTION my_subst;
DELIMITER $$
CREATE FUNCTION my_subst(str VARCHAR(255))
RETURNS VARCHAR(255)
BEGIN
DECLARE pos1 INT DEFAULT 0;
DECLARE pos2 INT DEFAULT 0;
DECLARE token VARCHAR(255);
DECLARE new_token VARCHAR(255);
label1: LOOP
SET pos1 = LOCATE('%%',str);
IF pos1 = 0 THEN
LEAVE label1;
END IF;
SET pos2 = LOCATE('%%',str,pos1+1);
IF pos2 = 0 THEN
LEAVE label1;
END IF;
SET token = SUBSTR(str,pos1,pos2-pos1+2);
SELECT blockcontent INTO new_token FROM descriptions WHERE blockname = token;
SET str = REPLACE(str,token,new_token);
END LOOP label1;
RETURN str;
END;
$$
DELIMITER ;
and then just use this function to do substitutions.