Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`dc_app_test`.`#sql-3ae4_3b`, CONSTRAINT `FK_2CE0D8114D5B19A3` FOREIGN KEY (`measurement_meetstaat_id`) REFEREN CES `meetstaat` (`id`)) 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.