python - SQLAlchemy 反射 : How do I query data from specific columns?

Question

使用SQLAlchemy反射，如何查询特定列的数据？

testtable = Table('member', Metadata, autoload=True)

def TestConnection():
    data = None
    loopCounter = 0 
    for data in session.query(testtable).filter_by(is_active=1, is_deleted=0): 
        print(loopCounter + 1, data)
        loopCounter += 1
    if data is None:
        raise Exception ("Could not find any data that matches your query")        
    else:
        print("It worked!")

TestConnection()

上面的查询为我提供了成员 表中所有列中的所有数据。然而，我想要的是从列中获取特定数据。例如。我想检索 username 和 password 列，但语法不正确。以下是我目前所拥有的:

def TestConnection():
    loopCounter = 0 
    for password, username in session.query(testtable).filter_by(is_active=1, is_deleted=0):
        print(loopCounter + 1, data)
        loopCounter += 1
    if data is None:
        raise Exception ("Could not find any data that matches your query")        
    else:
        print("It worked!")

失败并出现错误:

Traceback (most recent call last):
File "/home/workspace/upark/src/monitor.py", line 36, in <module>
TestConnection()
File "/home/workspace/upark/src/monitor.py", line 26, in TestConnection
for password, username in session.query(testtable).filter_by(is_active=1, is_deleted=0):
ValueError: too many values to unpack (expected 2)

我正在使用来自 Oracle 的 Python3.2、SQLAchemy0.8 和 mysqlconnector。

编辑:一些小的进步

刚刚发现我可以在返回所有结果后“过滤”出列，如下所示:

def TestConnection():
    data = None
    loopCounter = 0 
    for data in session.query(testtable).filter_by(is_active=1, is_deleted=0): 
        print(loopCounter + 1, data.password, data.username)
        loopCounter += 1
    if data is None:
        raise Exception ("Could not find any data that matches your query")        
    else:
        print("It worked!")

这将给出:

1 pass1 userone
2 pass2 usertwo

但如您所见，那是在我取回所有列之后。我想要的是只从我需要的列中获取数据。例如。 Members 表有 10 列。为了提高效率，我只需要从其中两个获取数据。

Answer 1

只需指定要选择的列 [session.query(testtable.c.password, testtable.c.username)] 而不是整个表 [session.query(testtable)]:

def TestConnection():
    data = None
    loopCounter = 0 
    for data in session.query(testtable.c.password, testtable.c.username).filter_by(is_active=1, is_deleted=0): 
        pwd, usr = data
        print(loopCounter + 1, pwd, usr)
        loopCounter += 1
    if data is None:
        raise Exception ("Could not find any data that matches your query")        
    else:
        print("It worked!")