There are three main things you can do to optimize your queries:
Add indexes. If you have a frequent query on an unindexed column, add an index. For more information about how MySQL uses indexing, refer to Chapter 18, "Optimizing Your Database." Remember though that although an appropriate index might speed up operations that need to find data in the table, keeping indexes up-to-date increases the time required to write data. Do not add indexes that will not be used.
Use ANALYZE TABLE . (See Chapter 18 for syntax.) This updates the information MySQL stores about key distribution. This information is used to decide the order in which tables are joined. If MySQL seems to be joining your tables in a strange order, try ANALYZE TABLE .
Use OPTIMIZE TABLE . (See Chapter 18 for syntax.) This defragments the table storage, sorts the indexes, and updates the table statistics as used by the query optimizer.
