SQLAlchemy ORM

Takeaways

SQLAlchemy ORM

• Lets you compose SQL expressions by mapping python classes of objects to tables in the database
• Is the highest layer of abstraction in SQLALchemy.
• Wraps the SQL Expressions and Engine to work together to interact with the database
• Will be used in this course, so we can know how to use ORM libraries in general.

Moreover, SQLAlchemy is split into two libraries:

• SQLAlchemy Core
• SQLAlchemy ORM (Object Relational Mapping library). SQLALchemy ORM is offered as an optional library, so you don't have to use the ORM in order to use the rest of SQLAlchemy.
  • The ORM uses the Core library inside
  • The ORM lets you map from the database schema to the application's Python objects
  • The ORM persists objects into corresponding database tables

SQLAlchemy Layers of Abstraction Overview (Diagram)

QUIZ QUESTION: :

Below are some of SQLAlchemy's layers of abstraction—can you match the description with the name?

ANSWER CHOICES:

Lowest layer of abstraction; looks a lot like interacting directly with a DB-API

Makes it possible to interact with any database management system, regardless of the SQL flavor used.

Avoids opening and closing connections for every data change

Lets you compose SQL statements by building Python objects

Highest level of abstraction; maps classes to tables.

Description	Which layer of abstraction?
The engine layer
The ORM layer
The dialect layer
The SQL expressions layer
The connection pool layer

SOLUTION:

Description	Which layer of abstraction?
The engine layer	Lowest layer of abstraction; looks a lot like interacting directly with a DB-API
The ORM layer	Highest level of abstraction; maps classes to tables.
The dialect layer	Makes it possible to interact with any database management system, regardless of the SQL flavor used.
The SQL expressions layer	Lets you compose SQL statements by building Python objects
The connection pool layer	Avoids opening and closing connections for every data change