PostgreSQL 11 introduced stored procedures that support transactions. Both are need for the connection in our relations.Ī drawback of user-defined functions is that they cannot perform transactions. The Foreign Key in AuthorBooks model is for the relations in the database and ‘relationship’ is for the Models in our Python application. N_pagess = int(input("number of pages in book? "))įirst_name = input("author's first name? ")Īdd_book(title, n_pagess, first_name, last_name)Įnter fullscreen mode Exit fullscreen mode Print("Input new book detail after '?':\n-") Pairing = AuthorBook(author_id = author.id, book_id = book.id) Pairing = AuthorBook(author_id = existing_author.id, book_id = book.id)Īuthor = Author(first_name = first_name, last_name = last_name) Session.flush() # we need to book id to be populated to the pairing N_pages = Column(Integer, nullable=False)Īuthor_id = Column(Integer, ForeignKey('authors.id'))īook_id = Column(Integer, ForeignKey('books.id'))ĭef add_book(title, n_pages, first_name, last_name):īook = Book(title = title, n_pages = n_pages)Įxisting_author = session.query(Author).filter(Author.first_name = first_name, Author.last_name = last_name).first() Id = Column(Integer, primary_key=True, autoincrement=True) # a catalog of classes and tables relative to that base - this is known as the declarative base class. Not_found_set = connection.execute(select_statement)įrom sqlalchemy import Column, Integer, String, ForeignKeyįrom sqlalchemy.orm import sessionmaker, relationshipįrom import declarative_baseĮngine = Classes mapped using the Declarative system are defined in terms of a base class which maintains Result_set = connection.execute(delete_statement) Update_statement = iris_table.update().where(iris_table.c.id = 151).values(sepallength = 4.9, petalwidth = 0.3)ĭelete_statement = iris_lete().where(iris_table.c.id = 151) Select_statement = iris_lect().where(iris_table.c.id = 151) Result_set = connection.execute(select_statement) Iris_table = Table('iris', meta, autoload = True, autoload_with = engine)
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