From time to time mySQL databases can get corrupt, whether it due to lack of disk space, power failure, or just an error.

Repairing MyISAM mySQL Tables/Databases:

cd /var/lib/mysql/DBNAME
#^ Please note that we assume your mySQL data directory is /var/lib/mysql

myisamchk *.MYI

Repairing ISAM mySQL Tables/Databases:

cd /var/lib/mysql/DBNAME
#^ Please note that we assume your mySQL data directory is /var/lib/mysql

isamchk *.MYI

(from internet)