Django框架中数据的连锁查询和限制返回数据的方法

>>> Publisher.objects.filter(country="U.S.A.").order_by("-name")
[<Publisher: O'Reilly>, <Publisher: Apress>]

SELECT id, name, address, city, state_province, country, website
FROM books_publisher
WHERE country = 'U.S.A'
ORDER BY name DESC;

>>> Publisher.objects.order_by('name')[0]
<Publisher: Apress>

SELECT id, name, address, city, state_province, country, website
FROM books_publisher
ORDER BY name
LIMIT 1;

>>> Publisher.objects.order_by('name')[0:2]

SELECT id, name, address, city, state_province, country, website
FROM books_publisher
ORDER BY name
OFFSET 0 LIMIT 2;

>>> Publisher.objects.order_by('name')[-1]
Traceback (most recent call last):
 ...
AssertionError: Negative indexing is not supported.

>>> Publisher.objects.order_by('-name')[0]