I’ve been having the same problem. I just noticed the following note at the very bottom of the Laravel Schema docs: Note: The field referenced in the foreign key is very likely an auto increment and therefore automatically an unsigned integer. Please make sure to create the foreign key field with unsigned() as both fields … Read more
Check that all your constraints are really spelled out correctly, also check that there’s not any other tables that uses the constraint names FK_userId or FK_blogId
Inspired by Eevee‘s comment: def get_class_by_tablename(tablename): “””Return class reference mapped to table. :param tablename: String with name of table. :return: Class reference or None. “”” for c in Base._decl_class_registry.values(): if hasattr(c, ‘__tablename__’) and c.__tablename__ == tablename: return c
There is a tiny performance hit on inserts, updates and deletes because the FK has to be checked. For an individual record this would normally be so slight as to be unnoticeable unless you start having a ridiculous number of FKs associated to the table (Clearly it takes longer to check 100 other tables than … Read more
You don’t need to pass the department id, the instance itself is enough. The following should work just fine: new_team = Team( nickname = team_name, employee_id = employee_id, department_id = Department.objects.get(password = password, department_name = department_name)) Just a note: don’t ever name your foreign fields something_id. That something is enough. Django is meant to make … Read more
You should make car_id a primary key in cars.
You have to define your TASK_CAT column first and then set foreign key on it. private static final String TASK_TABLE_CREATE = “create table ” + TASK_TABLE + ” (” + TASK_ID + ” integer primary key autoincrement, ” + TASK_TITLE + ” text not null, ” + TASK_NOTES + ” text not null, ” + … Read more
The reason foreign key constraints exist is to guarantee that the referenced rows exist. “The foreign key identifies a column or a set of columns in one table that refers to a column or set of columns in another table. The values in one row of the referencing columns must occur in a single row … Read more
I haven’t done this yet, but I used inspectdb to generate the models.py file from an existing DB that does exactly that – this is what inspectdb threw back, so it should work: creator = models.ForeignKey(Users, null=True, related_name=”creator”) assignee = models.ForeignKey(Users, null=True, related_name=”assignee”) Hope that works for you – if it doesn’t I am going … Read more
MongoDB doesn’t support server side foreign key relationships, normalization is also discouraged. You should embed your child object within parent objects if possible, this will increase performance and make foreign keys totally unnecessary. That said it is not always possible, so there is a special construct called DBRef which allows to reference objects in a … Read more