In your SQL query, add in an ORDER at the end, and order it by something that you know will make the records be in reverse order (such as an auto incrementing numerical ID or date the record was entered).
select * from mytable where field like '%blah%' order by ID desc limit 0,30
The limit parameter will also help you limit how many rows are returned, saving a bit of resources.
It kind of isn't an issue in MySQL, but a lot of rows in a table can slow performance. You can index fields in MySQL to make your queries run faster. If there is a field you are searching consistently, try indexing it and it will make your queries run faster.