product matching mysql scripts - regex fuzzy logic big data syntax

I require various scripts to match products to each other. You must have experience of building fast scripts for very large data including regex / syntax type scripts. We have 1 master table of products and approx 1000 separate tables with 'similar' products. We need to match / map around 50 million products from 1000s of separate retailers to our 1 main master table (around 3 million products). We need to find ways to match and link products to the master table, as all products have slightly different names, descriptions etc, and we need to find way to group all same products together. We would need a % score for each product to say how sure the script is that there is a match between our master table and any product from the other tables.