What is a Good Data Model?

To start off with, let us go over what a good data model looks like, what it doesn't look like and what maybe the benefits:

A well data modelled table should

1. Be able to retrieve data quickly
2. Be able to store data quickly
3. Be clear and easy to work with

This essentially what the book refers to as "Simple and Fast".

A well data modelled table should not

1. Store unneeded data
2. Need to change its rows very often **
3. Need too many JOINs to get you the data that you need

Purposes of a Data Model

A good data model should serve a specific and narrow set of purposes.

The more purposes the table serves the:

1. More indexes it would need.
2. More cumbersome it will be to store and keep in memory.
3. More overhead it would be to write to.
4. More likely it be a single-point-of-failure
5. More likely it would have locks and deadlocks
6. More likely it would be to add unneeded data
7. More difficult it would be to make changes to your application if you needed to make changes to the table.

If you notice a pattern here, you may notice that reusability to a high degree, may hinder the performance of a database. There needs to be a balance between reusability and single-responsibility of the data models to be effective. I shall write of way to achieve that balance in future chapters.

** A table that has data that needs to change often and is transient, may be better suited in a cache. If it needs to be saved and transactional, then a smaller table that records the state of certain keys or values with a combination of a log to store how it got that way if it is needed.