91 lines
2.7 KiB
Python
91 lines
2.7 KiB
Python
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"""
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Consultar objetos de la Base de Datos
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con ORM de SQLAlchemy
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"""
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from sqlalchemy import create_engine
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from sqlalchemy.ext.declarative import declarative_base
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from sqlalchemy import Column, Integer, String, Sequence
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from sqlalchemy.orm import sessionmaker
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from sqlalchemy.orm import aliased
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engine = create_engine('sqlite:///:memory:')
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Base = declarative_base()
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class Author(Base):
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__tablename__ = 'author'
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id = Column(Integer, Sequence('author_id_seq'), primary_key=True)
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firstname = Column(String)
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lastname = Column(String)
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def __repr__(self):
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return "{} {}".format(self.firstname, self.lastname)
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Base.metadata.create_all(engine)
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author = Author(firstname="Juanita", lastname='Leon')
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Session = sessionmaker(bind=engine)
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session = Session()
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session.add(author)
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session.add_all([Author(firstname='Joél Ez', lastname='Silva'),
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Author(firstname='Jorge', lastname='Olivares')])
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session.commit()
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"""
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QUERYs
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"""
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print("Query #1:")
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# Devuelve los Autores ordenados por ID.
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for instance in session.query(Author).order_by(Author.id):
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print(instance.firstname, instance.lastname)
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print("Query #2:")
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# Devuelve el Nombre y Apellido de cada Autor
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for firstname, lastname in session.query(Author.firstname, Author.lastname):
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print(firstname, lastname)
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print("Query #3:")
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# Devuelve el Autor, y su primer nombre
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for row in session.query(Author, Author.firstname).all():
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print(row.Author, row.firstname)
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print("Query #4:")
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# Devuelve los Autores, asignando una etiqueta al campo firsname
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for row in session.query(Author.firstname.label('firstname_label')).all():
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print(row.firstname_label)
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print("Query #5:")
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# Devuelve el Autor y su primer nombre, definiendo un alias de la tabla
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author_alias = aliased(Author, name='author_alias')
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for row in session.query(author_alias, author_alias.firstname).all():
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print(row.author_alias)
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print("Query #6:")
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# Busqueda de todos los Autores, filtrados por slices, del 2 al 3
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for an_author in session.query(Author).order_by(Author.id)[1:3]:
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print(an_author)
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print("Query #7:")
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# Filtrado por autores con nombre 'Joél Ez'
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for name, in session.query(Author.firstname).filter_by(firstname='Joél Ez'):
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print(name)
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print("Query #8:")
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# Filtrado por apellido del Autor
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for name, in session.query(Author.firstname).filter(Author.lastname == 'Silva'):
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print(name)
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print("Query #9:")
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# Filtrado por nombre de autor y apellido
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for an_author in session.query(Author).\
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filter(Author.firstname == 'Jorge').\
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filter(Author.lastname == 'Olivares'):
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print(an_author)
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print("Query #10")
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# Cantidad de autores con el nombre 'Juanita'
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print(session.query(Author).filter(Author.firstname == 'Juanita').count())
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