Fixed course/lecture deletion (#165)

db_schema.sql

@@ -231,7 +231,7 @@ CREATE TABLE IF NOT EXISTS `sorterrorlog_data` (
 );
 
 CREATE VIEW IF NOT EXISTS `courses` AS select * from `courses_data` where (not(`courses_data`.`deleted`));
-CREATE VIEW IF NOT EXISTS `lectures` AS select * from `lectures_data` where (not(`lectures_data`.`deleted`));
-CREATE VIEW IF NOT EXISTS `videos` AS select * from `videos_data` where (not(`videos_data`.`deleted`));
+CREATE VIEW IF NOT EXISTS `lectures` AS select `lectures_data`.* from `lectures_data` join `courses_data` on (`courses_data`.`id` = `course_id`) where (not(`lectures_data`.`deleted` or `courses_data`.`deleted`));
+CREATE VIEW IF NOT EXISTS `videos` AS select `videos_data`.* from `videos_data` join `lectures_data` on (`lectures_data`.`id` = `lecture_id`) join `courses_data` on (`courses_data`.`id` = `course_id`) where (not(`videos_data`.`deleted` or `lectures_data`.`deleted` or `courses_data`.`deleted`));
 CREATE VIEW IF NOT EXISTS `sorterrorlog` AS select * from `sorterrorlog_data` where (not(`sorterrorlog_data`.`deleted`));
 COMMIT;