Question

你好？我试图在SQLAlchemy中写一个查询（有2个子查询），但出现错误AttributeError：'list'对象没有属性'l_date'

这是我的代码：

import sqlalchemy as db
from sqlalchemy import func
from sqlalchemy import desc
from sqlalchemy.orm import sessionmaker
from sqlalchemy import or_
from sqlalchemy import and_
from sqlalchemy.sql.expression import  alias

try:

    engine = db.create_engine('postgresql://user:pass@localhost:5432/db_name')
    connection = engine.connect()

except:
    print('Error establishing DB connection')

# Import metadata
metadata = db.MetaData()

# create a configured "Session" class
Session = sessionmaker(bind=engine)

# create a Session
session = Session()

# Import articles, authors and log tables
log = db.Table('log', metadata, autoload=True, autoload_with=engine)


def days_with_request_errors():
    query1 = db.select([func.DATE(log.columns.time).label('l_date'), func.count(log.columns.status).label('s_count')]) \
        .where(or_(log.columns.status.like('%5%'), log.columns.status.like('%4%'))) \
        .group_by(func.DATE(log.columns.time))

    ResultProxy = connection.execute(query1)
    q1 = ResultProxy.fetchall()

    query2 = db.select([func.DATE(log.columns.time).label('l_date'),
                          func.count(log.columns.status).label('s_count')]) \
        .group_by(func.DATE(log.columns.time))

    ResultProxy = connection.execute(query2)
    q2 = ResultProxy.fetchall()

    main_query = db.select([q1.l_date, (q1.s_count * 100) / q2.s_count]) \
        .where(q1.l_date == q2.l_date) \
        .where(and_((q1.c.s_count * 100) / q2.c.s_count) > 1)

    ResultProxy = connection.execute(main_query)
    return ResultProxy.fetchall()

这是我正在转移到SQLAlchemy的原始SQL查询。（原始查询工作正常）：

SELECT q1.date, ((q1.count * 100) / q2.count) as percentage
  FROM (SELECT date(time) as date, COUNT(status) as count
        FROM log
        WHERE status LIKE '%4%' or status LIKE '%5%'
        GROUP BY date(time)) as q1,
       (SELECT date(time) as date, COUNT(status) as count
        FROM log
        GROUP BY date(time)) as q2
  WHERE q1.date = q2.date and ((q1.count * 100) / q2.count) > 1

任何帮助将不胜感激。

Answer 1

我弄清楚出了什么问题。子查询缺少别名。为了使其正常工作，我对子查询进行了如下修改：

query1 = db.select([func.DATE(log.columns.time).label('l_date'), func.count(log.columns.status).label('s_count')]) \
        .where(or_(log.columns.status.like('%5%'), log.columns.status.like('%4%'))) \
        .group_by(func.DATE(log.columns.time)).alias('query1')


    query2 = db.select([func.DATE(log.columns.time).label('l_date'),
                          func.count(log.columns.status).label('s_count')]) \
        .group_by(func.DATE(log.columns.time)).alias('query2')

SQLAlchemy子查询列表对象没有属性

1 个答案: