Description of ActiveRecord pattern from <Patterns of Enterprise Application Architecture>

gistfile1.txt

In simple applications the Domain Model (116) is an uncomplicated structure that actually corresponds pretty
closely to the database structure, with one domain class per database table. Such domain objects often have
only moderately complex business logic. In this case it makes sense to have each domain object be
responsible for loading and saving from the database, which is Active Record (160) (see Figure 3.3). Another
way to think of the Active Record (160) is that you start with a Row Data Gateway (152) and then add domain
logic to the class, particularly when you see repetitive code in multiple Transaction Scripts (110).

...

As the domain logic gets more complicated and you begin moving toward a rich Domain Model (116), the simple
approach of an Active Record (160) starts to break down.