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The Ultimate Python Database Toolkit: SQLAlchem...
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Kod.io Linz
March 01, 2014
Programming
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270
The Ultimate Python Database Toolkit: SQLAlchemy - Muhammet Sena Aydın
Kod.io Linz
March 01, 2014
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Transcript
SQLAlchemy SQLAlchemy The Python SQL Toolkit and Object Relational Mapper
SQLAlchemy SQLAlchemy Muhammet S. AYDIN Python Developer @ Metglobal @mengukagan
SQLAlchemy SQLAlchemy • No ORM Required • Mature • High
Performing • Non-opinionated • Unit of Work • Function based query construction • Modular
SQLAlchemy SQLAlchemy • Seperation of mapping & classes • Eager
loading & caching related objects • Inheritance mapping • Raw SQL
SQLAlchemy SQLAlchemy Drivers: PostgreSQL MySQL MSSQL SQLite Sybase Drizzle Firebird
Oracle
SQLAlchemy SQLAlchemy Core Engine Connection Dialect MetaData Table Column
SQLAlchemy SQLAlchemy Core Engine Starting point for SQLAlchemy app. Home
base for the database and it's API.
SQLAlchemy SQLAlchemy Core Connection Provides functionality for a wrapped DB-API
connection. Executes SQL statements. Not thread-safe.
SQLAlchemy SQLAlchemy Core Dialect Defnes the behavior of a specifc
database and DB-API combination. Query generation, execution, result handling, anything that differs from other dbs is handled in Dialect.
SQLAlchemy SQLAlchemy Core MetaData Binds to an Engine or Connection.
Holds the Table and Column metadata in itself.
SQLAlchemy SQLAlchemy Core Table Represents a table in the database.
Stored in the MetaData.
SQLAlchemy SQLAlchemy Core Column Represents a column in a database
table.
SQLAlchemy SQLAlchemy Core Creating an engine:
SQLAlchemy SQLAlchemy Core Creating tables Register the Table with MetaData.
Defne your columns. Call metadata.create_all(engine) or table.create(engine)
SQLAlchemy SQLAlchemy Core Creating tables
SQLAlchemy SQLAlchemy Core More on Columns Columns have some important
parameters. index=bool, nullable=bool, unique=bool, primary_key=bool, default=callable/scalar, onupdate=callable/scalar, autoincrement=bool
SQLAlchemy SQLAlchemy Core Column Types Integer, BigInteger, String, Unicode, UnicodeText,
Date, DateTime, Boolean, Text, Time and All of the SQL std types.
SQLAlchemy SQLAlchemy Core Insert insert = countries_table.insert().values( code='TR', name='Turkey') conn.execute(insert)
SQLAlchemy SQLAlchemy Core Select select([countries_table]) select([ct.c.code, ct.c.name]) select([ct.c.code.label('c')])
SQLAlchemy SQLAlchemy Core Select select([ct]).where(ct.c.region == 'Europe & Central Asia')
select([ct]).where(or_(ct.c.region.ilike('%euro pe%', ct.c.region.ilike('%asia%')))
SQLAlchemy SQLAlchemy Core Select A Little Bit Fancy select([func.count(ct.c.id).label('count'), ct.c.region]).group_by(ct.c.region).order_by('
count DESC') SELECT count(countries.id) AS count, countries.region FROM countries GROUP BY countries.region ORDER BY count DESC
SQLAlchemy SQLAlchemy Core Update ct.update().where(ct.c.id == 1).values(name='Turkey', code='TUR')
SQLAlchemy SQLAlchemy Core Cooler Update case_list = [(pt.c.id == photo_id,
index+1) for index, photo_id in enumerate(order_list)] pt.update().values(photo_order=case(case_list)) UPDATE photos SET photo_order=CASE WHEN (photos.id = :id_1) THEN :param_1 WHEN (photos.id = :id_2) THEN :param_2 END
SQLAlchemy SQLAlchemy Core Delete ct.delete().where(ct.c.id_in([60,71,80,97]))
SQLAlchemy SQLAlchemy Core Joins select([ct.c.name, dt.c.data]).select_from(ct.join(dt)).where(ct.c .code == 'TRY')
SQLAlchemy SQLAlchemy Core Joins select([ct.c.name, dt.c.data]).select_from(join(ct, dt, ct.c.id == dt.c.country_id)).where(ct.c.code
== 'TRY')
SQLAlchemy SQLAlchemy Core Func A SQL function generator with attribute
access. simply put: func.count() becomes COUNT().
SQLAlchemy SQLAlchemy Core Func select([func.concat_ws(“ -> “, ct.c.name, ct.c.code)]) SELECT
concat_ws(%(concat_ws_2)s, countries.name, countries.code) AS concat_ws_1 FROM countries
SQLAlchemy SQLAlchemy ORM - Built on top of the core
- Applied usage of the Expression Language - Class declaration - Table defnition is nested in the class
SQLAlchemy SQLAlchemy ORM Defnition
SQLAlchemy SQLAlchemy ORM Session Basically it establishes all connections to
the db. All objects are kept on it through their lifespan. Entry point for Query.
SQLAlchemy SQLAlchemy ORM Master / Slave Connection? master_session = sessionmaker(bind=engine1)
slave_session = sessionmaker(bind=engine2) Session = master_session() SlaveSession = slave_session()
SQLAlchemy SQLAlchemy ORM Querying Session.query(Country).flter(Country.name.s tartswith('Tur')).all() Session.query(func.count(Country.id)).one() Session.query(Country.name, Data.data).join(Data).all()
SQLAlchemy SQLAlchemy ORM Querying Session.query(Country).flter_by(id=1).updat e({“name”: “USA”}) Session.query(Country).flter(~Country.regio n.in_('Europe &
Central Asia')).delete()
SQLAlchemy SQLAlchemy ORM Relationships: One To Many
SQLAlchemy SQLAlchemy ORM Relationships: One To One
SQLAlchemy SQLAlchemy ORM Relationships: Many To Many
SQLAlchemy SQLAlchemy ORM Relationships: Many To Many
SQLAlchemy SQLAlchemy ORM Relationship Loading
SQLAlchemy SQLAlchemy ORM Relationship Loading
SQLAlchemy SQLAlchemy ORM More? http://sqlalchemy.org http://github.com/zzzeek/sqlalchemy irc.freenode.net #sqlalchemy