异步SQLAlchemy示例中的"meta“

from sqlalchemy import create_engine, MetaData, Table, Column, Integer, String

# 创建异步引擎
engine = create_engine('postgresql+asyncpg://user:password@localhost/mydatabase')

# 创建元数据
metadata = MetaData()

# 定义表结构
users = Table('users', metadata,
    Column('id', Integer, primary_key=True),
    Column('name', String),
    Column('age', Integer)
)

# 创建表
async with engine.begin() as conn:
    await conn.run_sync(metadata.create_all)

# 插入数据
async with engine.begin() as conn:
    await conn.execute(users.insert().values(name='John', age=25))

# 查询数据
async with engine.begin() as conn:
    result = await conn.execute(users.select())
    rows = await result.fetchall()
    for row in rows:
        print(row)