Django--filter()-字段查找(雙下劃線的使用詳解)

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?在了解django中的字段查找的同時，讓我們先熟悉一下比較符：

大于--gt-(greater than)　　小于--lt-(less than)　　等于--eq-(equal)　　大于等于--gte　　小于等于--lte

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>>> from queryset_demo.models import Blog,Author,Entry >>> entry = Entry.objects.filter(pub_date__lte='2017-01-01') >>> entry <QuerySet [<Entry: python-2015>, <Entry: python-2014>, <Entry: python-4>]> >>> [d.id for d in entry] # 返回數據的id [5, 6, 7]

對應的sql語句為

mysql> select * from queryset_demo_entry-> ; +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ | id | headline | body_text | pub_date | mod_date | n_comments | n_pingbacks | rating | blog_id | +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ | 1 | python | This is a demo | 2018-07-11 | 2018-07-14 | 10 | 29 | 23 | 4 | | 2 | python | django | 2018-07-12 | 2018-07-28 | 2 | 2 | 2 | 2 | | 3 | python-2017 | djagoddd | 2017-06-01 | 2017-08-14 | 55 | 676 | 88 | 3 | | 4 | python-2017 | django-ll | 2017-03-14 | 2017-07-14 | 22 | 33 | 44 | 1 | | 5 | python-2015 | ddd | 2015-07-14 | 2015-07-14 | 33 | 33 | 33 | 1 | | 6 | python-2014 | ddd | 2014-07-14 | 2014-07-14 | 22 | 33 | 33 | 3 | | 7 | python-4 | ddd | 2014-07-14 | 2018-07-04 | 66 | 66 | 66 | 4 | +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ 7 rows in set (0.00 sec)mysql> select * from queryset_demo_entry where pub_date<2017-01-01; Empty set, 1 warning (0.00 sec)mysql> select * from queryset_demo_entry where pub_date<'2017-01-01'; +----+-------------+-----------+------------+------------+------------+-------------+--------+---------+ | id | headline | body_text | pub_date | mod_date | n_comments | n_pingbacks | rating | blog_id | +----+-------------+-----------+------------+------------+------------+-------------+--------+---------+ | 5 | python-2015 | ddd | 2015-07-14 | 2015-07-14 | 33 | 33 | 33 | 1 | | 6 | python-2014 | ddd | 2014-07-14 | 2014-07-14 | 22 | 33 | 33 | 3 | | 7 | python-4 | ddd | 2014-07-14 | 2018-07-04 | 66 | 66 | 66 | 4 | +----+-------------+-----------+------------+------------+------------+-------------+--------+---------+ 3 rows in set (0.00 sec) 對應的sql語句

對外鍵ForeignKey的字段查找，同時也是一個特殊的地方就是可以通過單下劃線

>>> entry <QuerySet [<Entry: python>, <Entry: python-4>]> >>> type(entry) <class 'django.db.models.query.QuerySet'> >>> [d.id for d in entry] [1, 7]

sql

mysql> select * from queryset_demo_entry-> ; +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ | id | headline | body_text | pub_date | mod_date | n_comments | n_pingbacks | rating | blog_id | +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ | 1 | python | This is a demo | 2018-07-11 | 2018-07-14 | 10 | 29 | 23 | 4 | | 2 | python | django | 2018-07-12 | 2018-07-28 | 2 | 2 | 2 | 2 | | 3 | python-2017 | djagoddd | 2017-06-01 | 2017-08-14 | 55 | 676 | 88 | 3 | | 4 | python-2017 | django-ll | 2017-03-14 | 2017-07-14 | 22 | 33 | 44 | 1 | | 5 | python-2015 | ddd | 2015-07-14 | 2015-07-14 | 33 | 33 | 33 | 1 | | 6 | python-2014 | ddd | 2014-07-14 | 2014-07-14 | 22 | 33 | 33 | 3 | | 7 | python-4 | ddd | 2014-07-14 | 2018-07-04 | 66 | 66 | 66 | 4 | +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ 7 rows in set (0.00 sec) View Code

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精確查找exact

>>> entry=Entry.objects.get(body_text__exact="This is a demo") >>> entry.id 1>>> entry=Entry.objects.get(body_text="This is a demo") >>> entry.id 1

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sql

mysql> select * from queryset_demo_entry-> ; +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ | id | headline | body_text | pub_date | mod_date | n_comments | n_pingbacks | rating | blog_id | +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ | 1 | python | This is a demo | 2018-07-11 | 2018-07-14 | 10 | 29 | 23 | 4 | | 2 | python | django | 2018-07-12 | 2018-07-28 | 2 | 2 | 2 | 2 | | 3 | python-2017 | djagoddd | 2017-06-01 | 2017-08-14 | 55 | 676 | 88 | 3 | | 4 | python-2017 | django-ll | 2017-03-14 | 2017-07-14 | 22 | 33 | 44 | 1 | | 5 | python-2015 | ddd | 2015-07-14 | 2015-07-14 | 33 | 33 | 33 | 1 | | 6 | python-2014 | ddd | 2014-07-14 | 2014-07-14 | 22 | 33 | 33 | 3 | | 7 | python-4 | ddd | 2014-07-14 | 2018-07-04 | 66 | 66 | 66 | 4 | +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ 7 rows in set (0.00 sec)mysql> select * from queryset_demo_entry where body_text ='This is a demo'; +----+----------+----------------+------------+------------+------------+-------------+--------+---------+ | id | headline | body_text | pub_date | mod_date | n_comments | n_pingbacks | rating | blog_id | +----+----------+----------------+------------+------------+------------+-------------+--------+---------+ | 1 | python | This is a demo | 2018-07-11 | 2018-07-14 | 10 | 29 | 23 | 4 | +----+----------+----------------+------------+------------+------------+-------------+--------+---------+ 1 row in set (0.00 sec) View Code

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跨表查詢

>>> Entry.objects.filter(blog__name='blog_3') <QuerySet [<Entry: python>, <Entry: python-4>]> >>> entry=Entry.objects.filter(blog__name='blog_3') >>> [d.id for d in entry] [1, 7]

sql

mysql> select * from queryset_demo_blog; +----+-----------------+------------------------------+ | id | name | tagline | +----+-----------------+------------------------------+ | 1 | change_new_name | All the latest Beatles news. | | 2 | create_test | This is the wayof create | | 3 | Cheddar Talk | One to Many test | | 4 | blog_3 | this is a test | +----+-----------------+------------------------------+ 4 rows in set (0.00 sec)mysql> select * from queryset_demo_entry-> ; +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ | id | headline | body_text | pub_date | mod_date | n_comments | n_pingbacks | rating | blog_id | +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ | 1 | python | This is a demo | 2018-07-11 | 2018-07-14 | 10 | 29 | 23 | 4 | | 2 | python | django | 2018-07-12 | 2018-07-28 | 2 | 2 | 2 | 2 | | 3 | python-2017 | djagoddd | 2017-06-01 | 2017-08-14 | 55 | 676 | 88 | 3 | | 4 | python-2017 | django-ll | 2017-03-14 | 2017-07-14 | 22 | 33 | 44 | 1 | | 5 | python-2015 | ddd | 2015-07-14 | 2015-07-14 | 33 | 33 | 33 | 1 | | 6 | python-2014 | ddd | 2014-07-14 | 2014-07-14 | 22 | 33 | 33 | 3 | | 7 | python-4 | ddd | 2014-07-14 | 2018-07-04 | 66 | 66 | 66 | 4 | +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ 7 rows in set (0.00 sec) View Code

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反向查詢

通過blog表進行查詢

它也可以倒退。要引用“反向”關系，只需使用模型的小寫名稱即可。

這個例子檢索所有Blog具有至少一個對象Entry?，其headline包含'Lennon'：

>>> from queryset_demo.models import * >>> blog = Blog.objects.filter(entry__body_text__contains='dj') >>> blog <QuerySet [<Blog: create_test>, <Blog: Cheddar Talk>, <Blog: change_new_name>]> >>> [d.id for d in blog] [2, 3, 1] >>>

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跨越多值關系

使用下劃線查找多值得關系

>>> blog = Blog.objects.filter(entry__body_text__contains='dj') >>> blog <QuerySet [<Blog: create_test>, <Blog: Cheddar Talk>, <Blog: change_new_name>]> >>> [d.id for d in blog] [2, 3, 1] >>> blog = Blog.objects.filter(entry__body_text__contains='dj',entry__pub_date__year=2017) >>> [d.id for d in blog] [3, 1] >>> blog = Blog.objects.filter(entry__body_text__contains='dj').filter(entry__pub_date__year=2017) >>> blog_2 = Blog.objects.filter(entry__body_text__contains='dj').filter(entry__pub_date__year=2017) >>> blog_2 <QuerySet [<Blog: Cheddar Talk>, <Blog: change_new_name>]> >>> blog <QuerySet [<Blog: Cheddar Talk>, <Blog: change_new_name>]> >>>

英文：

　　Suppose there is only one blog that had both entries containing?“Lennon”?and entries from 2008, but that none of the entries from 2008 contained?“Lennon”. The first query would not return any blogs, but the 　　second query would return that one blog.

　　In the second example, the first filter restricts the queryset to all those blogs linked to entries with?“Lennon”?in the headline. The second filter restricts the set of blogs?further?to those that are also linked to entries that were published in 2008. The entries selected by the second filter may or may not be the same as the entries in the first filter. We are filtering the?Blog?items with each filter statement, not the?Entry?items.

理解：

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數據庫進行數據的添加

mysql> mysql> select * from queryset_demo_entry; +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ | id | headline | body_text | pub_date | mod_date | n_comments | n_pingbacks | rating | blog_id | +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ | 1 | python | This is a demo | 2018-07-11 | 2018-07-14 | 10 | 29 | 23 | 4 | | 2 | python | django | 2018-07-12 | 2018-07-28 | 2 | 2 | 2 | 2 | | 3 | python-2017 | djagoddd | 2017-06-01 | 2017-08-14 | 55 | 676 | 88 | 3 | | 4 | python-2017 | django-ll | 2017-03-14 | 2017-07-14 | 22 | 33 | 44 | 1 | | 5 | python-2015 | ddd | 2015-07-14 | 2015-07-14 | 33 | 33 | 33 | 1 | | 6 | python-2014 | ddd | 2014-07-14 | 2014-07-14 | 22 | 33 | 33 | 3 | | 7 | python-4 | ddd | 2014-07-14 | 2018-07-04 | 66 | 66 | 66 | 4 | | 8 | demo | demo | 2017-06-16 | 2017-05-16 | 33 | 33 | 5 | 2 | | 9 | demo2 | zzddxx | 2017-02-16 | 2017-02-04 | 44 | 33 | 22 | 3 | +----+-------------+----------------+------------+------------+------------+-------------+--------+---------+ 9 rows in set (0.00 sec)mysql> select * from queryset_demo_blog; +----+-----------------+------------------------------+ | id | name | tagline | +----+-----------------+------------------------------+ | 1 | change_new_name | All the latest Beatles news. | | 2 | create_test | This is the wayof create | | 3 | Cheddar Talk | One to Many test | | 4 | blog_3 | this is a test | +----+-----------------+------------------------------+ 4 rows in set (0.01 sec)

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shell進行測試

>>> blog = Blog.objects.filter(entry__body_text__contains='dj',entry__pub_date__year=2017) >>> blog <QuerySet [<Blog: Cheddar Talk>, <Blog: change_new_name>]> >>> >>> >>> blog_2 = Blog.objects.filter(entry__body_text__contains='dj').filter(entry__pub_date__year=2017) >>> blog_2 <QuerySet [<Blog: create_test>, <Blog: Cheddar Talk>, <Blog: Cheddar Talk>, <Blog: change_new_name>]> >>> [d.id for d in blog] [3, 1] >>> [d.id for d in blog_2] [2, 3, 3, 1]

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轉載于:https://www.cnblogs.com/Echo-O/p/9311891.html

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