Getting "django.db.utils.IntegrityError: FOREIGN KEY constraint failed

you are trying to either

1.insert a data which doesn't exist in foreign key table. like adding DepartmentId 4 to employee table but there is no departmentId 4 in department table.

2.Deleting a row from a table which is not cascaded and have dependency on foreign table like deleting department 3 but department 3 is related to many employee.

3.You are trying to add new columns to table directly.