The natural InnoDB type for NEWDECIMAL is FIXBINARY, not BINARY, since there probably is no benefit from stripping trailing bytes 0x20; note that tables created with 5.0.6 and containing DECIMAL do not need to be rebuilt, as BINARY works as well; note that because of Jani's fix to bug 10465, tables created with 5.0.? - 5.0.5 DO NEED TO BE REBUILT if they contain DECIMAL