SQLAlchemyでjoinする

2016/12/18 2017/07/23

PythonのSQLAlchemyでMySQLのテーブルをjoinするときの覚書です。

モデルクラスはこんな感じでrelationを書いておきます。
例として社員マスタテーブルと給与支払テーブルのrelationとします。

models.py

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.sql.schema import Column
from sqlalchemy.orm import relation
from sqlalchemy.schema import ForeignKey
from sqlalchemy.dialects.mysql.base import (
    VARCHAR,
    INTEGER,
    BIGINT
)

Base = declarative_base()

class Employee(Base):
    __tablename__ = 'employee'

    employee_id = Column(INTEGER(unsigned=False), primary_key=True,nullable=True)
    name = Column(VARCHAR(length=45), nullable=False)

    payroll_payment = relation(
        'PayrollPayment',
        backref = 'employee',
        order_by = 'PayrollPayment.employee_id'
    )

    def __repr__(self):
        return '<Employee(%d, %s)>' % (self.employee_id, self.name)

class PayrollPayment(Base):
    __tablename__ = 'payroll_payment'

    payroll_payment_id = Column(INTEGER(unsigned=False), primary_key=True,nullable=True)

    employee_id = Column(
        INTEGER(unsigned=False),
        ForeignKey('employee.employee_id'),
        nullable=False
    )

    salary = Column(BIGINT(unsigned=True), nullable=False)
    salary_month = Column(INTEGER(unsigned=True), nullable=False)

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy.sql.schema import Column

from sqlalchemy.orm import relation

from sqlalchemy.schema import ForeignKey

from sqlalchemy.dialects.mysql.base import (

VARCHAR,

INTEGER,

BIGINT

)

Base = declarative_base()

class Employee(Base):

__tablename__ = 'employee'

employee_id = Column(INTEGER(unsigned=False), primary_key=True,nullable=True)

name = Column(VARCHAR(length=45), nullable=False)

payroll_payment = relation(

'PayrollPayment',

backref = 'employee',

order_by = 'PayrollPayment.employee_id'

)

def __repr__(self):

return '' % (self.employee_id, self.name)

class PayrollPayment(Base):

__tablename__ = 'payroll_payment'

payroll_payment_id = Column(INTEGER(unsigned=False), primary_key=True,nullable=True)

employee_id = Column(

INTEGER(unsigned=False),

ForeignKey('employee.employee_id'),

nullable=False

)

salary = Column(BIGINT(unsigned=True), nullable=False)

salary_month = Column(INTEGER(unsigned=True), nullable=False)

この例ではouter joinとして結合します。

## configとかは省略します

url = 'mysql+pymysql://' + config.db_username + ':' + config.db_password + '@' + config.db_host + '/' + config.db_name + '?charset=utf8'
engine = create_engine(url,echo=True)
Session = sessionmaker(bind=engine)
session = Session()

employee_tbl = models.Employee

result = session.query(
    employee_tbl.employee_id,
    employee_tbl.name
).outerjoin(
    employee_tbl.payroll_payment
).all()