MYSQL INSERT or UPDATE IF

Question

Been looking around the web for a while now and don\'t seem to be able to come across anything similar to what I want. I know it\'s something to do with the way I\'m writing

Answer 1

Thanks to all the help from those above the solution I found in the end was very close to both. Find it below:

INSERT INTO `stock`
    (name, barcode, item, quantity, location, price, date)  
VALUES
    (?,?,?,?,?,?,?)                         
ON DUPLICATE KEY UPDATE
     quantity = CASE WHEN 
                VALUES(date) < $date
                THEN quantity + $quantity
                ELSE quantity 
                END,
    date = CASE WHEN 
                VALUES(date) < $date
                THEN VALUES(date)
                ELSE $date
                END