Corrupted MyISAM table in MySQL

Even if the MyISAM table format is very reliable (all the changes that the SQL statement makes to the table are written before the statement returns), you can still get the corrupted table if any of the following events occur:

· The mysqld process was killed in the middle of writing.

· Unexpected computer shutdown occurs (for example, the computer is turned off).

· Hardware failure.

· You can use external programs (such as MYISAMCHK) on tables that are being modified by the server at the same time.

· Software flaws in MySQL or MyISAM code.

A typical symptom of a damaged table is as follows:

· When you select data from a table, you get the following error:

· Incorrect key file for table: ' ... '. Try to repair it

· The query cannot find rows in the table or return incomplete data.

You can use the Check Table statement statement to check the health of the MyISAM table and repair a corrupted MyISAM table with repair table. When the mysqld is not running, you can also use the MYISAMCHK command to check or repair a table.

If your table becomes frequently damaged, you should try to determine why this is the case. The most important thing to understand is whether the table becomes corrupted because of the server crash. You can find the most recent restarted mysqld message in the error log to validate this early. If there is such a message, it is possible that the table corruption is a result of the server's death. Otherwise, the damage may occur during normal operation. This is a flaw. You should try to create a repeatable test case that shows the problem.