众所周知，直接明文写sql操作数据库有很多不安全的地方。
借助一个SQLAlchemy的工具来进行python对象和数据库数据的映射，这样达到操作python对象即可改变数据库的数据。
1 创建数据库
-- This is the file to create COMPANY table and to populate it with 7 records.
-- Just copy and past them on psql prompt.
DROP TABLE learn.COMPANY;
CREATE TABLE learn.COMPANY(
ID INT PRIMARY KEY NOT NULL,
NAME TEXT NOT NULL,
AGE INT NOT NULL,
ADDRESS CHAR(50),
SALARY REAL
);
INSERT INTO learn.COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (1, 'Paul', 32, 'California', 20000.00 );
INSERT INTO learn.COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (2, 'Allen', 25, 'Texas', 15000.00 );
INSERT INTO learn.COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (3, 'Teddy', 23, 'Norway', 20000.00 );
INSERT INTO learn.COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 );
INSERT INTO learn.COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (5, 'David', 27, 'Texas', 85000.00 );
INSERT INTO learn.COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (6, 'Kim', 22, 'South-Hall', 45000.00 );
INSERT INTO learn.COMPANY VALUES (7, 'James', 24, 'Houston', 10000.00 );2 基础使用
SQLAchemy的基础步骤为：
- 1 创建python对象和数据库表的映射（需要每一个column的对应关系），注意tablename和table_args。
- 2 创建session对象
- 2.1 创建引擎
- 2.2 绑定引擎到Sessionmaker
- 2.3 创建session
- 3 增删改查
我们首先查看一下数据库的数据。
我们先查询salary高于15000的人员：
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine, Column, Integer, String
Base = declarative_base()
class Company(Base):
__tablename__ = 'company'
__table_args__ = ({"schema": "learn"},)
id = Column(Integer, primary_key=True)
name = Column(String)
age = Column(Integer)
address = Column(String)
salary = Column(Integer)
engine = create_engine('postgresql+psycopg2://postgres:root@localhost:5432/crabboss')
DBSession = sessionmaker(bind=engine)
session = DBSession()
companies = session.query(Company).filter(Company.salary > 15000).all()
for company in companies:
print(f"id : {company.id:1} | name: {company.name:2} | age: {company.age:1} | address: {company.address:10} | salary: {company.salary:10}")
session.close()代码执行结果：
3 增
此处我们没有设置主线为SERIAL，故手工将id设置为8.
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine, Column, Integer, String
Base = declarative_base()
class Company(Base):
__tablename__ = 'company'
__table_args__ = ({"schema": "learn"},)
id = Column(Integer, primary_key=True, autoincrement=True)
name = Column(String)
age = Column(Integer)
address = Column(String)
salary = Column(Integer)
engine = create_engine('postgresql+psycopg2://postgres:root@localhost:5432/crabboss')
DBSession = sessionmaker(bind=engine)
session = DBSession()
# 插入
new_user = Company(id=8, name="Tom", age=20, address="San Francisco", salary=30000)
session.add(new_user)
session.commit()
# 查询
companies = session.query(Company).filter(Company.salary > 15000).all()
for company in companies:
print(f"id : {company.id:1} | name: {company.name:2} | age: {company.age:1} | address: {company.address:10} | salary: {company.salary:10}")
session.close()结果如下：
4 删
先进行查询，之后删除。
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine, Column, Integer, String
Base = declarative_base()
class Company(Base):
__tablename__ = 'company'
__table_args__ = ({"schema": "learn"},)
id = Column(Integer, primary_key=True, autoincrement=True)
name = Column(String)
age = Column(Integer)
address = Column(String)
salary = Column(Integer)
engine = create_engine('postgresql+psycopg2://postgres:root@localhost:5432/crabboss')
DBSession = sessionmaker(bind=engine)
session = DBSession()
# 插入
# new_user = Company(id=8, name="Tom", age=20, address="San Francisco", salary=30000)
# session.add(new_user)
# session.commit()
# 删除
session.query(Company).filter(Company.name=="Tom").delete()
session.commit()
# 查询
companies = session.query(Company).filter(Company.salary > 15000).all()
for company in companies:
print(f"id : {company.id:1} | name: {company.name:2} | age: {company.age:1} | address: {company.address:10} | salary: {company.salary:10}")
session.close()结果如下：
5 改
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine, Column, Integer, String
Base = declarative_base()
class Company(Base):
__tablename__ = 'company'
__table_args__ = ({"schema": "learn"},)
id = Column(Integer, primary_key=True, autoincrement=True)
name = Column(String)
age = Column(Integer)
address = Column(String)
salary = Column(Integer)
engine = create_engine('postgresql+psycopg2://postgres:root@localhost:5432/crabboss')
DBSession = sessionmaker(bind=engine)
session = DBSession()
# 插入
# new_user = Company(id=8, name="Tom", age=20, address="San Francisco", salary=30000)
# session.add(new_user)
# session.commit()
# 删除
# session.query(Company).filter(Company.name=="Tom").delete()
# session.commit()
# 修改
session.query(Company).filter(Company.name=="Paul").update({"salary":30000})
session.commit()
# 查询
companies = session.query(Company).filter(Company.salary > 15000).all()
for company in companies:
print(f"id : {company.id:1} | name: {company.name:2} | age: {company.age:1} | address: {company.address:10} | salary: {company.salary:10}")
session.close()修改后结果如下：
