Why did these DB errors occured ?

[veenuisthebest]

I got 3 different database errors today, I had never seen them before !! Just wanted to know why they occured ..

1.

Database error in vBulletin 3.7.0:

Invalid SQL:

		SELECT poll.*, thread.pollid, open, threadid, replycount, forumid 
		FROM poll AS poll
		INNER JOIN thread AS thread USING (pollid)
		
		WHERE open <> 10 AND visible = 1 AND active = 1
		 AND thread.forumid NOT IN(56)
		ORDER BY RAND() DESC;

MySQL Error   : Got error 28 from storage engine
Error Number  : 1030
Request Date  : Sunday, July 20th 2008 @ 08:03:10 PM
Error Date    : Sunday, July 20th 2008 @ 08:03:10 PM
Script        : http://www.***.com/forum/portal.php
Referrer      : http://www.***.org/forum/portal.php
IP Address    : 99.228.73.66
Username      : Unregistered
Classname     : vB_Database
MySQL Version :

2. (Looks like a hacking attempt, coz I have no such user)

Database error in vBulletin 3.7.0:

Invalid SQL:
SHOW COLUMNS FROM user LIKE 'username';

MySQL Error   : Got error 28 from storage engine
Error Number  : 1030
Request Date  : Sunday, July 20th 2008 @ 10:44:47 PM
Error Date    : Sunday, July 20th 2008 @ 10:44:48 PM
Script        : http://www.***.com/forum/register.php?do=addmember
Referrer      : http://www.***.com/forum/register.php
IP Address    : 209.67.216.138
Username      : teenmovienude
Classname     : vB_Database
MySQL Version :

3.

Database error in vBulletin 3.7.0:

Invalid SQL:


    SELECT imageid, images.title, filename, thumbname, originalname, extension, images.catid  ,images.userid, images.username, images.description, images.dateline, images.views, posts ,width, height, originalwidth, originalheight ,filesize, originalfilesize, images.lastpostdateline, images.lastpostuserid, images.lastpostusername, votenum, votetotal

    FROM ppgal_images AS images

    

    WHERE  valid = 1 

AND images.catid IN (4)



AND images.thumbname != ''





    ORDER BY RAND()

    LIMIT 4;

MySQL Error   : Got error -1 from storage engine
Error Number  : 1030
Request Date  : Monday, July 21st 2008 @ 12:24:15 AM
Error Date    : Monday, July 21st 2008 @ 12:24:16 AM
Script        : http://www.***.com/forum/portal.php
Referrer      : 
IP Address    : 74.6.8.88
Username      : Unregistered
Classname     : vB_Database
MySQL Version :

Thanks