SQL to SQLAlchemy Model

What is SQL to SQLAlchemy?

SQL to SQLAlchemy turns CREATE TABLE statements into classic SQLAlchemy declarative models — a class(Base) per table with __tablename__ and Column(...) attributes, the declarative_base() style used across most existing SQLAlchemy 1.x projects.

How it works

Each SQL type maps to a SQLAlchemy column type — INTEGER/SERIAL → Integer, VARCHAR(n) → String(n), DECIMAL(p,s) → Numeric(p, s) (preserving precision and scale rather than collapsing to a lossy Float), TIMESTAMP → DateTime, UUID → String(36). Unlike the JS/TS generators in this cluster, a foreign key becomes a real, functional ForeignKey('table.column') argument directly inside Column(...) — SQLAlchemy models foreign keys as a column-level constraint, not a separate relation object, so this translation is unambiguous and safe to generate. primary_key=True, autoincrement=True, nullable=False, and unique=True are added from the parsed constraints. Only literal defaults and CURRENT_TIMESTAMP/NOW() (→ default=datetime.utcnow, with from datetime import datetime added automatically) are translated into default= arguments.

Features

• One class(Base) model per table, with __tablename__ set to the real SQL name
• Real, working ForeignKey('table.column') generation for referenced columns
• Numeric(precision, scale) preserved from DECIMAL/NUMERIC instead of a lossy float
• Literal and utcnow defaults translated; everything else left as a comment
• Copy or download the generated .py module

Example

Input:

CREATE TABLE users (
  id SERIAL PRIMARY KEY,
  external_id UUID DEFAULT uuid_generate_v4(),
  name VARCHAR(255) NOT NULL,
  is_active BOOLEAN DEFAULT true
);

CREATE TABLE posts (
  id SERIAL PRIMARY KEY,
  user_id INTEGER NOT NULL REFERENCES users(id),
  title VARCHAR(255) NOT NULL,
  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

Output:

from sqlalchemy import Column, Boolean, DateTime, ForeignKey, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from datetime import datetime

Base = declarative_base()


class User(Base):
    __tablename__ = 'users'

    id = Column(Integer, primary_key=True, autoincrement=True)
    external_id = Column(String(36))  # SQL default not translated: uuid_generate_v4()
    name = Column(String(255), nullable=False)
    is_active = Column(Boolean, default=True)


class Post(Base):
    __tablename__ = 'posts'

    id = Column(Integer, primary_key=True, autoincrement=True)
    user_id = Column(Integer, ForeignKey('users.id'), nullable=False)
    title = Column(String(255), nullable=False)
    created_at = Column(DateTime, default=datetime.utcnow)

Common errors

A DEFAULT expression the generator doesn't recognize, like uuid_generate_v4(), is left as a # SQL default not translated: uuid_generate_v4() comment rather than a guessed default= value — add the real behavior yourself, e.g. default=lambda: str(uuid.uuid4()) or a server-side default via server_default=text(...). Note that while ForeignKey is generated for you, the higher-level relationship() accessor (e.g. posts = relationship('Post', back_populates='user')) is not — that still requires you to decide the attribute name and back-reference on both classes. The generator also targets the classic declarative_base() API, not SQLAlchemy 2.0's typed Mapped/mapped_column style, so on a 2.0 codebase you'll need to convert the Column(...) lines by hand.

Best practices

Add relationship() calls immediately after pasting the models in, using the generated ForeignKey columns as your map of what needs one. Run alembic revision --autogenerate (or your migration tool of choice) against the models to catch any type mismatch with the real database before applying.