if you check the mysql logs and see a error code such as error 24

you can lookup the code by using the perror command

perror 24

A fatal error has occurred
DB Error: connect failed
Details have been logged for the administrator

create a symlink to the mysql.sock from the /tmp/ folder example
cd /tmp
ln -s /usr/local/lib/mysql.sock mysql.sock

Reference

http://ushost.name/training/repairing_a_mysql_database.htm

http://dev.mysql.com/doc/refman/5.0/en/repair-table.html

http://dev.mysql.com/doc/refman/5.0/en/repair.html

http://www.informit.com/articles/article.aspx?p=29406&seqNum=3

IBM Helpdesk

The number following the message indicates a database problem. The error number is generated by joomla! and error numbers 1, 2 and 3 indicate the following:

Error 1 = FATAL ERROR: MySQL support not available.
Error 2 = FATAL ERROR: Connection to database server failed.
Error 3 = FATAL ERROR: Database not found

my view in plain speak would be:

error 1
Joomla! attempts to talk with mysql on the server and fails to even talk to it – this might be because the server does not have mysql installed at all or maybe it is not configured correctly

technically: function_exists( ‘mysql_connect’ ) FAILS

error 2
sql is installed but for some reason we cannot login to mysql (this is where it tries the host, username, password stuff) – may indicate that these details are wrong in your config

technically: $this->_resource = @mysql_connect( $host, $user, $pass ) FAILS

mysqlshow –status db_name   * show engine type , and some other info

mysqlcheck -r dbname – repairs a table/database

describe tablename

reference

http://dev.mysql.com/doc/refman/5.0/en/show-table-status.html

innodb engine

http://dev.mysql.com/doc/refman/5.0/en/innodb-configuration.html

http://dev.mysql.com/doc/refman/5.0/en/innodb-monitor.html