So what kind of performance did you get from the query in my post #8?
I forgot to mention something: A condition that uses LIKE can *NOT* use an index, except in the specialized case of
WHERE field LIKE 'xxx%'
That is, where the only % wild card character is at the end of the string to match via LIKE.
So your query is FORCING MySQL to do a COMPLETE scan of the entire OFFERS table.
And that's why it's slow. And why it would be hard to make it faster.
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.