dbis-schema-creator 0.1.0

RWTH Aachen Computer Science i5/dbis assets for Lecture Datenbanken und Informationssysteme

DBIS Schema Creator

Create a schema for SQLite databases and populate it using object-oriented programming. Also draw the corresponding er-diagram.

Installation

pip install dbis-schema-creator

Usage

from schema_creator import *

from erdiagram import ER

from faker import Faker
fake = Faker()


# Create a Table object (sqlalchemy style)
class Users(Table):
	# Create tables
	user_id = Column(Integer, primary_key=True)
	username = Column(String(50))

	# Optionally set the table name. Default is the lowercase class name
	__tablename__ = 'users'

	# Specify how to populate the table (e.g., using faker or random)
	def populate(session, seed=None):
		for _ in range(100):
			user = Users(username=fake.name())
			session.add(user)

	# Specify how to draw the er-diagram
	def to_er_diagram():
		g = ER()
		g.add_node("User")
		g.add_attribute("User", "user_id", isPK=True)
		g.add_attribute("User", "username")
		return g


class Posts(Table):
	post_id = Column(Integer, primary_key=True)
	user_id = Column(Integer, ForeignKey('users.user_id'))
	text = Column(String(1000))

	depedencies = {Users} # specify the tables that this table depends on. Default is none

	def populate(session, seed=None):
		# get already populated user table
		users = session.query(Users).all()
		for _ in range(1000):
			user = random.choice(users)
			post = Posts(user_id=user.user_id, text=fake.text())
			session.add(post)

	def to_er_diagram():
		g = ER()
		g.add_node("Post", isWeak=True)
		g.add_attribute("Post", "post_id", isPK=True, isWeak=True)
		g.add_attribute("Post", "user_id")
		g.add_attribute("Post", "text")
		g.add_relation("User", "posts", "Post", "1", "m", isWeak=True)
		return g


# Create the schema factory
tables = {Users, Posts}
factory = SchemaFactory(tables)

# populate the table
factory.populate()

# create the schema
schema = factory.to_sql()

# create the er-diagram
er_diagram = factory.to_er_diagram()

# draw the er diagram
digraph = er_diagram.draw()
digraph.render('er-diagram', format='png', view=True)