Error Code: 1452. Cannot add or update a child row: a foreign key constraint fails (`mydb`.`course`, CONSTRAINT `fk_course_department1` FOREIGN KEY (`department_id`) REFERENCES `department` (`department_id`)) code example

Example: mysql error 1452

SELECT child_table.* 
FROM child_table 
LEFT JOIN parent_table 
  ON parent_table.referenced_column = child_table.referencing_column 
WHERE parent_table.referenced_column IS NULL


-- Delete all data from output of that query