What are the generated files when creating a table in MySQL (.opt, .frm, .MYD, .MYI)

When I create a database in MySQL and create a table called flat in it, 4 files are generated:

 db.opt
 flats.frm
 flats.MYD
 flats.MYI

This happens every time a table is created. What are these files?

Answer

The file db.opt contains the database characteristics. It is updated every time the database is altered.

For the remaining 3 files:

• table.frm – Describes the table’s format (it is created regardless of the storage engine being used)
• table.MYI – Contains the MyISAM table index information (created for MyISAM storage engine)
• table.MYD – Contains the MyISAM table data (created for MyISAM storage engine)