This documentation is for an older version. If you're using the most current version, select the documentation for that version with the version switch in the upper right corner of the online documentation, or by downloading a newer PDF or EPUB file. Disadvantages of Creating Many Tables in the Same Database

If you have many MyISAM tables in the same database directory, open, close, and create operations are slow. If you execute SELECT statements on many different tables, there is a little overhead when the table cache is full, because for every table that has to be opened, another must be closed. You can reduce this overhead by increasing the number of entries permitted in the table cache.