Even though the MyISAM table format is very reliable (all changes to a table made by an SQL statement are written before the statement returns), you can still get corrupted tables if any of the following events occur:
* The mysqld process is killed in the middle of a write.
* An unexpected computer shutdown occurs (for example, the computer is turned off).
* Hardware failures.
* You are using an external program (such as myisamchk) to modify a table that is being modified by the server at the same time.
* A software bug in the MySQL or MyISAM code.