MyBB SQL Error

MyBB has experienced an internal SQL error and cannot continue.

SQL Error:
1194 - Table 'mybb_users' is marked as crashed and should be repaired
Query:
SELECT uid, username, birthday, birthdayprivacy, usergroup, displaygroup FROM mybb_users WHERE birthday LIKE '%-6-%' OR birthday LIKE '%-6' OR birthday LIKE '%-5-%' OR birthday LIKE '%-5' OR birthday LIKE '%-7-%' OR birthday LIKE '%-7'