8.3.1.1 Speed of SELECT Statements

In general, when you want to make a slow SELECT ... WHERE query faster, the first thing to check is whether you can add an index. All references between different tables should usually be done with indexes. You can use the EXPLAIN statement to determine which indexes are used for a SELECT. See Section 8.2.1, “Optimizing Queries with EXPLAIN”, and Section 8.5.1, “How MySQL Uses Indexes”.

Some general tips for speeding up queries on MyISAM tables: