Database query error

I have 3 Dolphin accounts, all are giving Database query error. Below is the error I receive, the other 2 accounts only say Database query error

Database query error
SELECT `id`, `user_id`, `data` FROM `sys_sessions` WHERE `id`='' LIMIT 1
Table './sys_sessions' is marked as crashed and should be repaired

I'm using ver 7.1.4 where I get this error

Database query error
SELECT `id`, `user_id`, `data` FROM `sys_sessions` WHERE `id`='' LIMIT 1
Table './sys_sessions' is marked as crashed and should be repaired

The other 2 ver are 7.1.5 and 7.2.1

There are some solutions on the following page:
http://stackoverflow.com/questions/4357270/php-is-marked-as-crashed-and-should-be-repaired

Follow the guide to repair the table.  If it continues to crash, come back to this post and we will work on it.

Thank you very much Zigstum and GeekGirl, the information you gave me fixed the problem.

I used up all the storage on my server, would lack of storage space caused this problem?

Yes, it can. But you should have also been getting other errors as well which should have indicated space problems.