Corrupt SQL file how to restore?

why this error occurs? like and failure was not, and cleaning the antivirus.
Database error in vBulletin 3.8.4:
Invalid SQL:
SELECT
IF(votenum >= 1, votenum, 0) AS votenum,
IF(votenum >= 1 AND votenum > 0, votetotal / votenum, 0) AS voteavg,
post.pagetext AS preview,
thread.threadid, thread.title AS threadtitle, thread.forumid, pollid, open, postusername, postuserid, thread.iconid AS threadiconid,
thread.dateline, notes, thread.visible, sticky, votetotal, thread.attach, thread.lastpost, thread.lastposter, thread.lastpostid, thread.replycount, IF(thread.views<=thread.replycount, thread.replycount+1, thread.views) AS views,
thread.prefixid, thread.taglist, hiddencount, deletedcount
, NOT ISNULL(subscribethread.subscribethreadid) AS issubscribed
, deletionlog.userid AS del_userid, deletionlog.username AS del_username, deletionlog.reason AS del_reason
, threadredirect.expires
FROM vb_thread AS thread
LEFT JOIN vb_deletionlog AS deletionlog ON(thread.threadid = deletionlog.primaryid AND deletionlog.type = 'thread')
LEFT JOIN vb_subscribethread AS subscribethread ON(subscribethread.threadid = thread.threadid AND subscribethread.userid = 1 AND canview = 1)
LEFT JOIN vb_post AS post ON(post.postid = thread.firstpostid)
LEFT JOIN vb_threadredirect AS threadredirect ON(thread.open = 10 AND thread.threadid = threadredirect.threadid)
WHERE thread.threadid IN (0,9839,6392,6391,1981,1473,88,1375)
ORDER BY sticky DESC, lastpost DESC;
SQL Error : Table './klon/vb_post' is marked as crashed and should be repaired
Error Number : 145
IP Address : 90.188.220.91
Username : xD
Classname : vB_Database
SQL Version : 5.1.54