How do you fix a MySQL "Incorrect key file" error when you can't repair the table?

You'll need to run this command from the MySQL prompt:

REPAIR TABLE tbl_name USE_FRM;

From MySQL's documentation on the Repair command:

The USE_FRM option is available for use if the .MYI index file is missing or if its header is corrupted. This option tells MySQL not to trust the information in the .MYI file header and to re-create it using information from the .frm file. This kind of repair cannot be done with myisamchk.

Your query is generating a result set so large that it needs to build a temporary table either to hold some of the results or some intermediate product used in generating the result.

The temporary table is being generated in /var/tmp. This temporary table would appear to have been corrupted. Perhaps the device the temporary table was being built on ran out of space. However, usually this would normally result in an "out of space" error. Perhaps something else running on your machine has clobbered the temporary table.

Try reworking your query to use less space, or try reconfiguring your database so that a larger or safer partition is used for temporary tables.

MySQL Manual - B.5.4.4. Where MySQL Stores Temporary Files

Make sure that the server is running. If it is not, clients cannot connect to it. For example, if an attempt to connect to the server fails with a message such as one of those following, one cause might be that the server is not running:

$> mysql
ERROR 2003: Can't connect to MySQL server on 'host_name' (111)
$> mysql
ERROR 2002: Can't connect to local MySQL server through socket
'/tmp/mysql.sock' (111)

It might be that the server is running, but you are trying to connect using a TCP/IP port, named pipe, or Unix socket file different from the one on which the server is listening. To correct this when you invoke a client program, specify a --port option to indicate the proper port number, or a --socket option to indicate the proper named pipe or Unix socket file. To find out where the socket file is, you can use this command:

$> netstat -ln | grep mysql

After a fresh installation, if you try to log on to the server as root without using a password, you might get the following error message.

$> mysql -u root 
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

It means a root password has already been assigned during installation and it has to be supplied. See Section 2.10.4, “Securing the Initial MySQL Account” on the different ways the password could have been assigned and, in some cases, how to find it. If you need to reset the root password, see instructions in Section B.3.3.2, “How to Reset the Root Password”. After you have found or reset your password, log on again as root using the --password (or -p) option:

$> mysql -u root -p
Enter password:

If a client program receives the following error message when it tries to connect, it means that the server expects passwords in a newer format than the client is capable of generating:

$> mysql
Client does not support authentication protocol requested
by server; consider upgrading MySQL client