ALTER TABLE `student_by_course` 
ADD COLUMN `date_start_sbc` DATE NULL AFTER `status_stc`,
ADD COLUMN `date_end_sbc` DATE NULL AFTER `date_start_sbc`;
ALTER TABLE `observation` 
ADD COLUMN `status_osb` ENUM('ACTIVE','INACTIVE') NULL DEFAULT 'ACTIVE' AFTER `observation_osb`;

// fechas de inicio y fin del año lectivo
update student_by_course set date_start_sbc='2015-08-24',date_end_sbc='2016-07-15' where status_stc='ACTIVE';