Getting Started with SQLAlchemy ORM — Creating Tables (2/5)

Unlike Core, we will not use metadata, but declarative_base which will have metadata. When we access metadata, it works the same way as in Core.

Declarative Base

We start by creating a Base class that we will use for defining tables.

from sqlalchemy.orm import DeclarativeBase

class Base(DeclarativeBase):
    pass

Table

Now we create a class that will inherit from the Base class. Using __tablename__, we define how the table will be named in the database.

Then we define the fields on the class. If we want the column in the database to have the same name as the field, we don't need to specify the column name in Column as in Core. The rest in Column remains the same as in Core.

from sqlalchemy import Column, Integer, Text

class User(Base):
    __tablename__ = "users"

    id = Column(Integer, primary_key=True)
    first_name = Column(Text, nullable=True)
    last_name = Column(Text, nullable=True)

If we want to create tables, we can use the metadata on the Base class.

Base.metadata.drop_all(engine)
Base.metadata.create_all(engine)

It is also possible to create and delete classes one by one. In such a case, we do not use metadata on the Base, but directly use the class (User) and call __table__.create/drop on it.

User.__table__.create(engine, checkfirst=True)
User.__table__.drop(engine, checkfirst=True)