ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`tiny_university_updated`.`enroll`, CONSTRAINT `enroll_ibfk_1` FOREIGN KEY (`CLASS_CODE`) REFERENCES `class` (`CLASS_CODE`)) code example

Example: integrity constraint violation: 1452 cannot add or update a child row: a foreign key constraint fails

It just simply means that the value for column project_id on table comments you are inserting doesn't exist on table projects. Bear in mind that the values of column project_id on table comments is dependent on the values of ID on table Projects.

The value 50dc845a-83e4-4db3-8705-5432ae7aaee3 you are inserting for column project_id does not exist on table projects.