SqlAlchemy Python。 MySQLからの私はSQLAlchemyの隣にMySQLのコードを変換するにはどうすればよいSQLAlchemyの

Question

へ：

 SELECT 
       u.id AS writer_id, 
       u.user_login AS user_login, 
       m.message_id AS message_id, 
       m.message, 
       m.time 
      FROM 
       (SELECT 
        message_id, tm.writer_id, tm.receiver_id, message, time 
       FROM 
        test_messages tm 
       WHERE 
        (tm.writer_id = 1 AND tm.receiver_id = 2) 
         OR (tm.writer_id = 2 AND tm.receiver_id = 1) 
       ORDER BY tm.time DESC 
       LIMIT 10 OFFSET 0) AS m 
        LEFT JOIN 
       users u ON u.id = m.writer_id 
      ORDER BY (m.time); 

私は次の試みた：

s = select([ 
    users.c.id, 
    users.c.user_login, 
    messages.c.message_id, 
    messages.c.message, 
    messages.c.time 
]).select_from(
    select([ 
     messages.c.message_id, 
     messages.c.writer_id, 
     messages.c.receiver_id, 
     messages.c.message, 
     messages.c.time 
    ]).where(
     or_(
      and_(
       messages.c.writer_id == writer_id, 
       messages.c.receiver_id == receiver_id 
      ), 
      and_(
       messages.c.writer_id == receiver_id, 
       messages.c.receiver_id == writer_id 
      ) 
     ) 
    ).select_from(
     users.outerjoin(messages, users.c.id == messages.c.writer_id) 
    ).order_by(messages.c.time.desc()) 
).order_by(messages.c.time) 

response = await conn.execute(s) 

headers = response.keys() 
rows = await response.fetchall()  

はエイリアスの問題を持ちます。
pymysql.err.InternalError: (1248, 'Every derived table must have its own alias')
サブクエリ全体を書きましたが、エイリアスに問題があります。明示的にエイリアスを設定すべきか、何をすべきですか？ お願いします。あなたと同等のクエリを形成することができるCore and the SQL Expression Languageを使用して

Answer 1

の場合：

In [25]: subq = messages.select().\ 
    ...:  where(or_(
    ...:   and_(
    ...:    messages.c.writer_id == writer_id, 
    ...:    messages.c.receiver_id == receiver_id 
    ...:  ), 
    ...:   and_(
    ...:    messages.c.writer_id == receiver_id, 
    ...:    messages.c.receiver_id == writer_id 
    ...:  ) 
    ...: )).\ 
    ...:  order_by(messages.c.time.desc()).\ 
    ...:  limit(10).\ 
    ...:  alias() 

In [26]: s = select([users.c.id, 
    ...:    users.c.user_login, 
    ...:    subq.c.message_id, 
    ...:    subq.c.message, 
    ...:    subq.c.time]).\ 
    ...:  select_from(
    ...:   subq. 
    ...:   outerjoin(users, users.c.id == subq.c.writer_id)).\ 
    ...:  order_by(subq.c.time) 

はalias()の使用に注意してください。あなたの元のSQLは、あなたのクエリ構築の試みと比べて、別の方法で結合していました。元のSQLに従ってきました。