SQLAlchemy教程-第二章-SQL常用查询的ORM写法

Posted 2020-11-21 notfresh

今天是2018-07-02.
今天来写一些常用的SQL查询的ORM写法.

1. 先把Emp, 也就是员工表的模型补上.

class Emp(Base):
    __tablename__ = ‘emp‘
    empno = Column(Integer, primary_key=True)
    ename = Column(String(10))
    job = Column(String(9))
    mgr = Column(Integer)
    hiredate = Column(Date)
    comm = Column(DECIMAL(7, 2))
    deptno = Column(Integer, ForeignKey(‘dept.deptno‘))

    def __repr__(self):  # 定义这个方法是为了方便打印到控制台查看.
        return str({
            ‘empno‘: self.empno,
            ‘ename‘: self.ename,
            ‘job‘: self.job,
            ‘deptno‘: self.deptno
        })

1. 接下来, 我们进行一些基本的查询.

from models import *

def query_emp():
    emp1 = sess.query(Emp).first()
    print(emp1)


# 查询名字叫Smith的员工
def query_emp_with_filter():
    emp1 = sess.query(Emp).filter(Emp.ename == ‘Smith‘).first()
    print(emp1)


# 查询名字叫Smith, 职务为CLERK的一个员工
def query_emp_with_filters():
    emp1 = sess.query(Emp).filter(Emp.ename == ‘Smith‘, Emp.job == ‘CLERK‘).first()
    print(emp1)


# 查询职务为CLERK的全部员工
def query_emp_all_clerks():
    emp_clerks = sess.query(Emp).filter(Emp.job == ‘CLERK‘).all()
    for clerk in emp_clerks:
        print(clerk)


# 查询员工的名字和工号, 并按入职日期排序
def query_emp_empno_ename_order_by_hiredate():
    emps = sess.query(Emp.empno, Emp.ename, Emp.job, Emp.hiredate).order_by(Emp.hiredate.asc()).all()
    for item in emps:
        print(item.empno, item.ename, item.job, item.hiredate)

if __name__ == ‘__main__‘:
    query_emp_empno_ename_order_by_hiredate()

今天限于时间, 先这么多. 讲解比较粗劣, 各位同学有问题, 请留言.

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SQLAlchemy官方网站
http://docs.sqlalchemy.org/en/latest/contents.html
教程全部代码github地址
https://github.com/notfresh/sqlalchemy_demo