1. 返回列表和标量(Scalar)
前面我们注意到Query对象可以返回可迭代的值(iterator value)，然后我们可以通过for in来查询。不过Query对象的all()、one()以及first()方法将返回非迭代值(non-iterator value)，比如说all()返回的是一个列表：
> query = session.query(User).> filter(User.name.like('%ed')).order_by(User.id)
> query.all()
SELECT users.id AS users_id,
users.name AS users_name,
users.fullname AS users_fullname,
users.password AS users_password
FROM users
WHERE users.name LIKE "htmlcode">
> query.first()
SELECT users.id AS users_id,
users.name AS users_name,
users.fullname AS users_fullname,
users.password AS users_password
FROM users
WHERE users.name LIKE "htmlcode">
> from sqlalchemy.orm.exc import MultipleResultsFound
> try:
... user = query.one()
... except MultipleResultsFound, e:
... print e
SELECT users.id AS users_id,
users.name AS users_name,
users.fullname AS users_fullname,
users.password AS users_password
FROM users
WHERE users.name LIKE "htmlcode">
> for user in session.query(User).... filter("id<224").... order_by("id").all():
... print user.name
SELECT users.id AS users_id,
users.name AS users_name,
users.fullname AS users_fullname,
users.password AS users_password
FROM users
WHERE id<224 ORDER BY id
()
ed
wendy
mary
fred
当然很多人可能会和我感觉一样，会有些不适应，因为使用ORM就是为了摆脱SQL语句的，没想到现在又看到SQL的影子了。呵呵，SQLAlchemy也要照顾到使用上的灵活性嘛，毕竟有些查询语句直接编入要容易得多。
当然绑定参数也可以用基于字符串的SQL指派，使用冒号来标记替代参数，然后再使用params()方法指定相应的值：
> session.query(User).filter("id<:value and name=:name").... params(value=224, name='fred').order_by(User.id).one()
SELECT users.id AS users_id,
users.name AS users_name,
users.fullname AS users_fullname,
users.password AS users_password
FROM users
WHERE id<User('fred','Fred Flinstone', 'blah')>
到这里，SQL语句的样子已经初见端倪了，其实我们可以更极端一点，直接使用SQL语句，什么？这样就失去ORM的价值了！别急，这里只是介绍一下支持这种用法，当然我建议不到万不得已，尽量不要这样写，因为可能会有兼容的问题，毕竟各个数据库的SQL方言不一样。不过有一点需要注意的是，如果要直接使用原生SQL语句，在被query()所查询的映射类中，你必须保证语句所指代的列仍然被映射类所管理，比如接下来的例子：
> session.query(User).from_statement(
... "SELECT * FROM users where name=:name").... params(name='ed').all()
SELECT * FROM users where name="htmlcode">
> session.query("id", "name", "thenumber12").... from_statement("SELECT id, name, 12 as "
... "thenumber12 FROM users where name=:name").... params(name='ed').all()
SELECT id, name, 12 as thenumber12 FROM users where name="htmlcode">
> session.query(User).filter(User.name.like('%ed')).count()
SELECT count(*) AS count_1
FROM (SELECT users.id AS users_id,
users.name AS users_name,
users.fullname AS users_fullname,
users.password AS users_password
FROM users
WHERE users.name LIKE "htmlcode">
> from sqlalchemy import func
> session.query(func.count(User.name), User.name).group_by(User.name).all()
SELECT count(users.name) AS count_1, users.name AS users_name
FROM users GROUP BY users.name
()
[(1, u'ed'), (1, u'fred'), (1, u'mary'), (1, u'wendy')]
对于刚才提到的简单SELECT count(*) FROM table语句，我们可以通过下面的例子来实现：
> session.query(func.count('*')).select_from(User).scalar()
SELECT count("htmlcode">
> session.query(func.count(User.id)).scalar()
SELECT count(users.id) AS count_1
FROM users
()
4