old_contents: import asyncio
  import sqlalchemy as sa
  
  from aiomysql.sa import create_engine
  
  
  metadata = sa.MetaData()
  
  tbl = sa.Table('tbl', metadata,
                 sa.Column('id', sa.Integer, primary_key=True),
                 sa.Column('val', sa.String(255)))
  
  
  async def create_table(engine):
      async with engine.acquire() as conn:
          await conn.execute('DROP TABLE IF EXISTS tbl')
          await conn.execute('''CREATE TABLE tbl (
                                id serial PRIMARY KEY,
                                val varchar(255))''')
  
  
  async def go(loop):
      engine = await create_engine(user='root', db='test_pymysql',
                                   host='127.0.0.1', password='', loop=loop)
      await create_table(engine)
      async with engine.acquire() as conn:
          await conn.execute(tbl.insert().values(val='abc'))
          await conn.execute(tbl.insert().values(val='xyz'))
  
          async for row in conn.execute(tbl.select()):
              print(row.id, row.val)
  
          await conn.commit()
  
      engine.close()
      await engine.wait_closed()
  
  
  loop = asyncio.get_event_loop()
  loop.run_until_complete(go(loop))
  
new_contents: import asyncio
  import sqlalchemy as sa
  
  from aiomysql.sa import create_engine
  
  
  metadata = sa.MetaData()
  
  tbl = sa.Table('tbl', metadata,
                 sa.Column('id', sa.Integer, primary_key=True),
                 sa.Column('val', sa.String(255)))
  
  
  async def create_table(engine):
      async with engine.acquire() as conn:
          await conn.execute('DROP TABLE IF EXISTS tbl')
          await conn.execute('''CREATE TABLE tbl (
                                id serial PRIMARY KEY,
                                val varchar(255))''')
  
  
  async def go(loop):
      engine = await create_engine(user='root', db='test_pymysql',
                                   host='127.0.0.1', password='', loop=loop)
      await create_table(engine)
      async with engine.acquire() as conn:
          await conn.execute(tbl.insert().values(val='abc'))
          await conn.execute(tbl.insert().values(val='xyz'))
  
          async for row in conn.execute(tbl.select()):
              print(row.id, row.val)
  
          await conn.execute("commit")
  
      engine.close()
      await engine.wait_closed()
  
  
  loop = asyncio.get_event_loop()
  loop.run_until_complete(go(loop))
  
subject: Update example_simple_sa.py (#308)