see http://www.howtoforge.com/forums/showthread.php?p=299049

mrtnzlml

2013-07-26 4c12c10c58529cd80a34e820caee06ef8754a7aa

1
ALTER TABLE  `sys_session` CHANGE  `session_id`  `session_id` VARCHAR( 64 ) CHARACTER SET latin1 COLLATE latin1_swedish_ci NOT NULL;