Sqlalchemy primary key without auto-increment

Sqlalchemy primary key without auto-increment

In SQLAlchemy, you can define a primary key without auto-increment by using the primary_key parameter of the Column class and setting its autoincrement parameter to False. This is useful when you want to provide your own unique identifiers for the primary key values.

Here's how you can define a primary key without auto-increment using SQLAlchemy:

from sqlalchemy import create_engine, Column, Integer, String from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker Base = declarative_base() class MyTable(Base): __tablename__ = 'my_table' id = Column(Integer, primary_key=True, autoincrement=False) # Primary key without auto-increment name = Column(String) # Create a SQLite in-memory database engine = create_engine('sqlite:///:memory:', echo=True) # Create the table in the database Base.metadata.create_all(engine) # Create a session Session = sessionmaker(bind=engine) session = Session() # Add a record with a custom primary key value record = MyTable(id=1001, name='Item A') session.add(record) session.commit() # Query the record queried_record = session.query(MyTable).filter_by(id=1001).first() print(queried_record.id, queried_record.name) # Close the session and dispose the engine session.close() engine.dispose()

In this example, the id column is defined as the primary key without auto-increment by setting primary_key=True and autoincrement=False in the Column definition. This allows you to provide your own values for the primary key.

Remember that when using a primary key without auto-increment, you're responsible for ensuring the uniqueness and assignment of primary key values when inserting records into the table.

Examples

  1. SQLAlchemy Define Primary Key Without Auto-Increment

    • This query demonstrates how to define a primary key without auto-increment in SQLAlchemy.
    from sqlalchemy import create_engine, Column, Integer, String from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Product(Base): __tablename__ = 'products' id = Column(Integer, primary_key=True, autoincrement=False) # No auto-increment name = Column(String, nullable=False) engine = create_engine('sqlite:///:memory:') Base.metadata.create_all(engine)

  2. SQLAlchemy Insert with Non-Auto-Increment Primary Key

    • This query shows how to insert records with a primary key that is not auto-incrementing.
    from sqlalchemy.orm import sessionmaker Session = sessionmaker(bind=engine) session = Session() # Insert with a specific primary key value product1 = Product(id=1, name="Product A") session.add(product1) session.commit()

  3. SQLAlchemy Composite Primary Key Without Auto-Increment

    • This query discusses how to define a composite primary key without auto-increment.
    from sqlalchemy import ForeignKey class OrderItem(Base): __tablename__ = 'order_items' order_id = Column(Integer, ForeignKey('orders.id'), primary_key=True, autoincrement=False) product_id = Column(Integer, ForeignKey('products.id'), primary_key=True, autoincrement=False) quantity = Column(Integer)

  4. SQLAlchemy Define Custom Primary Key

    • This query demonstrates how to define a primary key with a custom data type without auto-increment.
    class CustomID(Base): __tablename__ = 'custom_ids' custom_id = Column(String(10), primary_key=True, autoincrement=False) description = Column(String)

  5. SQLAlchemy Generate Primary Key Manually

    • This query shows how to manually generate primary key values to avoid auto-increment.
    import uuid # Generate UUID-based primary key class User(Base): __tablename__ = 'users' id = Column(String, primary_key=True, autoincrement=False) name = Column(String) user = User(id=str(uuid.uuid4()), name="John Doe") session.add(user) session.commit()

  6. SQLAlchemy Use Non-Auto-Increment Primary Key in Relationships

    • This query discusses how to set up relationships with non-auto-increment primary keys.
    class Order(Base): __tablename__ = 'orders' order_id = Column(String, primary_key=True, autoincrement=False) class OrderItem(Base): __tablename__ = 'order_items' id = Column(Integer, primary_key=True) order_id = Column(String, ForeignKey('orders.order_id')) order = Order(order_id="ORD001") session.add(order) session.commit()

  7. SQLAlchemy Handle Duplicates with Non-Auto-Increment Primary Key

    • This query explores how to handle duplicates when working with non-auto-increment primary keys.
    from sqlalchemy.exc import IntegrityError # Attempt to add a duplicate primary key duplicate_order = Order(order_id="ORD001") try: session.add(duplicate_order) session.commit() except IntegrityError: session.rollback() # Handle duplicate key

  8. SQLAlchemy Primary Key Without Auto-Increment and Unique Constraints

    • This query discusses how to define unique constraints with primary keys that are not auto-incrementing.
    class Customer(Base): __tablename__ = 'customers' customer_id = Column(Integer, primary_key=True, autoincrement=False) email = Column(String, unique=True) # Enforce unique constraint on email # Inserting customers with unique email addresses customer1 = Customer(customer_id=101, email="customer1@example.com") customer2 = Customer(customer_id=102, email="customer2@example.com")

  9. SQLAlchemy Reuse Primary Key Without Auto-Increment

    • This query demonstrates how to reuse or reset primary keys in a non-auto-increment setup.
    # Delete a record and reuse its primary key product_to_delete = session.query(Product).filter_by(id=1).first() if product_to_delete: session.delete(product_to_delete) session.commit() reused_product = Product(id=1, name="Reused Product") session.add(reused_product) session.commit()

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