Django中manytomanyField自定义第三张表
2021/10/16 23:11:19
本文主要是介绍Django中manytomanyField自定义第三张表,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
自定义第三张表:
# models.py class Boy(models.Model): name = models.CharField(max_length=32) class Girl(models.Model): name = models.CharField(max_length=32) class Love(models.Model): b = models.ForeignKey('Boy') g = models.ForeignKey('Girl') # 创建联合唯一索引 # class Meta: # unique_together = [ # ('b','g'), # ] # views.py def test(request): # objs = [ # models.Boy(name='summer'), # models.Boy(name='spring'), # models.Boy(name='autumn'), # ] # models.Boy.objects.bulk_create(objs,5) # objs = [ # models.Girl(name='小于'), # models.Girl(name='小秋'), # models.Girl(name='小夏'), # ] # models.Girl.objects.bulk_create(objs,5) # 查询和girl小于有关系的boy # 1 通过girl表进行反向查找 obj = models.Girl.objects.filter(name='小于').first().love_set.all() # obj = models.Girl.objects.filter(name='小于').first().love_set.select_related('b').all() for i in obj: print(i.b.name) print(' '.center(60,'=')) # 2 通过Love表进行查找 obj = models.Love.objects.filter(g__name='小于').all() for i in obj: print(i.b.name) # 这样进行查询性能不好,需要重新发sql请求在进行查询另外一张表中的数据 boy_list = models.Love.objects.filter(g__name='小于').values('b__name') for i in boy_list: print(i['b__name']) # 这样 进行了 优化 不会重复发送sql请求,查询到的结果内是字典 boy_obj = models.Love.objects.filter(g__name='小于').select_related('b').all() for i in boy_obj: print(i.b.name) # select_related('ut') 相当 于 inner join 先连成一张表再进行查询 return HttpResponse('insert ok ....')
ManyToManyField
# models.py from django.db import models class Boy(models.Model): name = models.CharField(max_length=32) # m = models.ManyToManyField('Girl') class Girl(models.Model): name = models.CharField(max_length=32) m = models.ManyToManyField('Boy') # views.py def test(request): # objs = [ # models.Boy(name='summer'), # models.Boy(name='spring'), # models.Boy(name='autumn'), # ] # models.Boy.objects.bulk_create(objs,5) # objs = [ # models.Girl(name='小于'), # models.Girl(name='小秋'), # models.Girl(name='小夏'), # ] # models.Girl.objects.bulk_create(objs,5) # ManyToManyField obj = models.Girl.objects.filter(name='小秋').first() # 增 # obj.m.add(3) # obj.m.add(3,4) # obj.m.add(*[1,2]) # 删 # obj.m.remove(3) # obj.m.remove(3,4) # obj.m.remove(*[1,2]) # 改 # obj.m.set([1,2,]) # boy_obj = obj.m.all() # for row in boy_obj: # print(row.id,row.name) # 清除 # obj.m.clear() # 反向查 在没有 ManyToManyField 字段的表中查 obj = models.Boy.objects.filter(name='summer').first() girl_obj = obj.girl_set.all() # 增删改查 obj.girl_set.set([1,2,3]) for row in girl_list: print(row.id,row.name) return HttpResponse('ok')
自定义第三张表+ManyToManyField
# modles.py class Boy(models.Model): name = models.CharField(max_length=32) class Girl(models.Model): name = models.CharField(max_length=32) m = models.ManyToManyField('Boy',through='Love',through_fields=('b','g')) # 只让其生成3张表,如果不加后面产生生成4张表 class Love(models.Model): b = models.ForeignKey('Boy') g = models.ForeignKey('Girl') # views.py def test(request): obj = models.Girl.objects.filter(name='小于').first() # obj.m.add(1) # 不行 # obj.m.remove(1) # 不行 # obj.m.set([1,2]) # 不行 # obj.m.clear() # 可以 # obj.m.all() # 可以 # 杂交的方法对获取查询方便点,还添加了清空功能 boy_obj = obj.m.all() for i in boy_obj: print(i.name)
这篇关于Django中manytomanyField自定义第三张表的文章就介绍到这儿,希望我们推荐的文章对大家有所帮助,也希望大家多多支持为之网!
- 2024-09-21MongoDB资料:新手入门与初级应用指南
- 2024-09-20MongoDB教程:初学者必备指南
- 2024-09-05MongoDB入门:快速掌握NoSQL数据库基础
- 2024-08-28go 项目中怎么打印调试-icode9专业技术文章分享
- 2024-08-21swoole未来的发展前景与golang对比哪个更好-icode9专业技术文章分享
- 2024-08-16goland 已经下了中文插件了, 怎么设置成中文-icode9专业技术文章分享
- 2024-07-26使用 SendGrid 的 Go 客户端库能同时给多个邮箱发吗-icode9专业技术文章分享
- 2024-07-26使用 SendGrid 的 Go 客户端库时怎么设置header 和 标签tag 呢-icode9专业技术文章分享
- 2024-07-26SendGrid 对邮件的类别(Categories)和标签的数量有限制吗?-icode9专业技术文章分享
- 2024-07-17课程推荐《高性能GO企业级APM监控系统实战》