from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base

DATABASE_URL = "postgresql://fastapi:Sj89061189@localhost/fastapi"

engine = create_engine(DATABASE_URL)
#不会提交事务  不会自动刷新  不会预加载
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

#ORM 模型都将继承自 Base
Base = declarative_base()

def get_db():
    #创建一个数据库会话
    db = SessionLocal()
    #发送异常正确关闭
    try:
        yield db
    finally:
        db.close()