Django干货知识分享，ORM模型(五)（orid模型例子）

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多对多关系

使用ManyToManyField，例如用户表、语言表和关系表

class Language(models.Model):
    title = models.CharField(max_length=20)
    users = models.ManyToManyField(User)

    def __str__(self) -> str:
        return '{0}'.format(self.title)

新增数据

>>> from myproject.myapp.models import User, Language
>>> user1 = User(first_name = '张', last_name = '三')
>>> user1.save()
(0.009) INSERT INTO "myapp_user" ("first_name", "last_name") VALUES ('张', '三'); args=['张', '三']
>>> user2 = User(first_name='李', last_name='四')
>>> user2.save()
(0.003) INSERT INTO "myapp_user" ("first_name", "last_name") VALUES ('李', '四'); args=['李', '四']
>>> user3 = User(first_name='王', last_name='五')
>>> user3.save()
(0.003) INSERT INTO "myapp_user" ("first_name", "last_name") VALUES ('王', '五'); args=['王', '五']
>>> language1 = Language(title='Java')
>>> language1.save()
(0.007) INSERT INTO "myapp_language" ("title") VALUES ('Java'); args=['Java']
>>> language2 = Language(title='Php')
>>> language2.save()
(0.003) INSERT INTO "myapp_language" ("title") VALUES ('Php'); args=['Php']
>>> language3 = Language(title='Python')
>>> language3.save()
(0.006) INSERT INTO "myapp_language" ("title") VALUES ('Python'); args=['Python']
>>> language1.users.add(user1)
(0.000) BEGIN; args=None
(0.005) INSERT OR IGNORE INTO "myapp_language_users" ("language_id", "user_id") SELECT 1, 5; args=(1, 5)
>>> language2.users.add(user1, user2)
(0.000) BEGIN; args=None
(0.004) INSERT OR IGNORE INTO "myapp_language_users" ("language_id", "user_id") SELECT 2, 5 UNION ALL SELECT 2, 6; args=(2, 5, 2, 6)
>>> language3.users.add(user1, user2, user3)
(0.000) BEGIN; args=None
(0.001) INSERT OR IGNORE INTO "myapp_language_users" ("language_id", "user_id") SELECT 3, 5 UNION ALL SELECT 3, 6 UNION ALL SELECT 3, 7; args=(3, 5, 3, 6, 3, 7)

查询数据

>>> Language.objects.filter(users__first_name='张', users__last_name='三')
(0.002) SELECT "myapp_language"."id", "myapp_language"."title" FROM "myapp_language" INNER JOIN "myapp_language_users" ON ("myapp_language"."id" = "myapp_language_users"."language_id") INNER JOIN "myapp_user" ON ("myapp_language_users"."user_id" = "myapp_user"."id") WHERE ("myapp_user"."first_name" = '张' AND "myapp_user"."last_name" = '三') LIMIT 21; args=('张', '三')
<QuerySet [<Language: Java>, <Language: Php>, <Language: Python>]>
>>> User.objects.filter(language__id=3)
(0.000) SELECT "myapp_user"."id", "myapp_user"."first_name", "myapp_user"."last_name" FROM "myapp_user" INNER JOIN "myapp_language_users" ON ("myapp_user"."id" = "myapp_language_users"."user_id") WHERE "myapp_language_users"."language_id" = 3 LIMIT 21; args=(3,)
<QuerySet [<User: 张 三>, <User: 李 四>, <User: 王 五>]>

删除数据

>>> Language.objects.filter(id=1).delete()
(0.000) SELECT "myapp_language"."id", "myapp_language"."title" FROM "myapp_language" WHERE "myapp_language"."id" = 1; args=(1,)
(0.000) BEGIN; args=None
(0.007) DELETE FROM "myapp_language_users" WHERE "myapp_language_users"."language_id" IN (1); args=(1,)
(0.000) DELETE FROM "myapp_language" WHERE "myapp_language"."id" IN (1); args=(1,)
(2, {'myapp.Language_users': 1, 'myapp.Language': 1})
>>> User.objects.filter(id=7).delete()
(0.000) SELECT "myapp_user"."id", "myapp_user"."first_name", "myapp_user"."last_name" FROM "myapp_user" WHERE "myapp_user"."id" = 7; args=(7,)
(0.000) BEGIN; args=None
(0.001) DELETE FROM "myapp_info" WHERE "myapp_info"."user_id" IN (7); args=(7,)
(0.001) DELETE FROM "myapp_language_users" WHERE "myapp_language_users"."user_id" IN (7); args=(7,)
(0.001) DELETE FROM "myapp_article" WHERE "myapp_article"."user_id" IN (7); args=(7,)
(0.000) DELETE FROM "myapp_user" WHERE "myapp_user"."id" IN (7); args=(7,)
(2, {'myapp.Language_users': 1, 'myapp.User': 1})

修改数据

>>> Language.objects.filter(title='Python').update(title='Python3')
(0.008) UPDATE "myapp_language" SET "title" = 'Python3' WHERE "myapp_language"."title" = 'Python'; args=('Python3', 'Python')
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Django干货知识分享，ORM模型（四）