Should you make a self-referencing table column a foreign key?

Question

For example to create a hierarchy of categories you use a column \'parent_id\', which points to another category in the same table.

Should this be a foreign key? Wha

Answer 1

Yes you should.

Advantages (as for any foreign key):

• Ensures that parent_id references a real row in the table
• Prevents accidental deletion of a parent that has children, or ensures that the delete cascades to delete the children also
• Provides information the optimizer can use

I can't think of any real disadvantages.