PostgreSQL学习

PostgreSQL 的学习及简单的使用示例

准备工作， 下载依赖安装sqlalchemy

pip install sqlalchemy

使用 sql 语句建表

from sqlalchemy import event
from sqlalchemy.orm import sessionmaker
from sqlalchemy import Table, Column, String, MetaData, create_engine, Integer

# 创建一个数据库链接引擎 
engine = create_engine("postgresql+psycopg2://scott:tiger@host/dbname")
# # 创建一个 DBSession
# DB_Session = sessionmaker(bind=engine)
# session = DB_Session()
meta = MetaData(engine)
note_table = Table(
    "note",     # table name 
    meta,
    Column('name', String, default="*"),
    Column('age', Integer)
    
)
# 建立对应的数据库链接
with engine.connect() as eng :
    # 表创建
    note_table.create()
    # 表插入数据
    set_info= note_table.insert().values(title='name', age=23)
    # 提交事物
    eng.execute(set_info)
    # 数据查询
    select_statement = note_table.select()
    result_set = eng.execute(select_statement)
    for r in result_set:
        print(r)
    # 数据修改
    update_statement = note_table.update().where(note_table.c.age=="17").values(title="Some2016Film")
    eng.execute(update_statement)
    # 数据删除
    delete_statement = note_table.delete().where(note_table.c.age == "22")
    eng.execute(delete_statement)

使用 orm 操作 sql

from sqlalchemy import create_engine  
from sqlalchemy import Column, String  
from sqlalchemy.ext.declarative import declarative_base  
from sqlalchemy.orm import sessionmaker

# 创建一个数据库链接引擎 
engine = create_engine("postgresql+psycopg2://scott:tiger@host/dbname")
# # 创建一个 DBSession
DB_Session = sessionmaker(bind=engine)
session = DB_Session()
DataBase = declarative_base()
class Note(DataBase):
    # 设置表名
    __tablename__ = 'notes'
    title = Column(String, primary_key=True)
    text = Column(String)

# 创建表结构并插入新的数据
note_info = Note(title=str(44), text=str('34657'))
session.add(note_info)
session.commit()

# 数据获取
notes = session.query(Note)  
for note in notes:  
    print(note.title)
# 数据修改
note_info.title = "Some2016Film"  
session.commit()
# 数据删除
session.delete(note_info)
session.commit()