SQL databases, persistence, and objects
When using SQLite, we will use a relational database with an access layer based on the SQL language. The SQL language is a legacy from an era when object-oriented programming was a rarity. The SQL language is heavily biased towards procedural programming, creating what's termed an impedance mismatch between the relational model of data and the object model of data. Within SQL databases, we generally focus on three tiers of data modeling, which are shown here:
Conceptual model: These are the entities and relationships implied by the SQL model. In most cases, these can map to Python objects and should correspond with the data model layer of the application tier. This is the place where an Object-Relational Mapping layer is useful.
Logical model: These are the tables, rows, and columns that appear to be in the SQL database. We'll address these entities in our SQL data manipulation statements. We say that these appear to exist because they're implemented...
