What to consider when deciding to use Single Table Inheritance

Question

I'm getting ready to start a small project that provides an opportunity to use single table inheritance. As I read through prior post on STI on Stackoverflow there seems to be some strong opinions on sides of the argument.

My application is related to my horse racing hobby. A horse's connections are defined as its current jockey, trainer and owner. The jockey, trainer and owner could be modeled using three separate tables (models/classes) or as one one class with several sub-classes through single table inheritance.

When faced with a decision like this, is there a check list of questions that one can go through to determine what approach is preferable. I'm assuming that using STI would reduce the number of potential joins. What are the other practical considerations?

Answer 1

There are a few things you should think about:

1. Are the objects, conceptually, children of a single parent?
   Don't use single table inheritance just because your classes share some attributes; make sure there is actually an OO inheritance relationship between each of them and an understandable parent class.
2. Do you need to do database queries on all objects together?
   If you want to list the objects together or run aggregate queries on all of the data, you’ll probably want everything in the same database table for speed and simplicity.
3. Do the objects have similar data but different behavior?
   If you have a larger number of model-specific columns, you should consider polymorphic associations instead.

The article linked goes in depth a bit more.