>>> 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 ? ORDER BY users.id
('%ed',)
[User('ed','Ed Jones', 'f8s7ccs'), User('fred','Fred Flinstone', 'blah')]
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first()方法限制并仅作为标量返回结果集的第一条记录：
>>> 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 ? ORDER BY users.id
LIMIT ? OFFSET ?
('%ed', 1, 0)
<User('ed','Ed Jones', 'f8s7ccs')>
>>> 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 ? ORDER BY users.id
('%ed',)
Multiple rows were found for one()
>>> from sqlalchemy.orm.exc import NoResultFound
>>> try:
... user = query.filter(User.id == 99).one()
... except NoResultFound, 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 ? AND users.id = ? ORDER BY users.id
('%ed', 99)
No row was found for one()
>>> 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
>>> 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')>
>>> session.query(User).from_statement(
... "SELECT * FROM users where name=:name").\
... params(name='ed').all()
SELECT * FROM users where name=?
('ed',)
[<User('ed','Ed Jones', 'f8s7ccs')>]
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我们还可以在query()中直接使用列名来指派我们想要的列而摆脱映射类的束缚：
>>> 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=?
('ed',)
[(1, u'ed', 12)]
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3. 计数 (Counting)
对于Query来说，计数功能也有个单独的方法称为count()：
>>> 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 ?) AS anon_1
('%ed',)
2
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count()方法被用于确定返回的结果集中有多少行，让我们观察一下产生的SQL语句，SQLAlchemy先是取出符合条件的所有行集合，然后再通过SELECT count(*)来统计有多少行。当然有点SQL知识的同学可能知道这条语句可以以更精简的方式写出来，比如SELECT count(*) FROM table，当然现代版本的SQLAlchemy不会去揣摩这样的想法。
>>> 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')]
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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(?) AS count_1
FROM users
('*',)
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