MySQL Errors

MySQL Errors :

• MySQL Error 1215: Cannot add foreign key constraint
• MySQL error 1449: The user specified as a definer does not exist
• MySql server startup error 'The server quit without updating PID file '
• Error 1005 Can't create table (errno 121)
• Error 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)