django(八)之数据库表的一对多,多对多表-增删改查
单表操作 表记录的添加 方式一: Book() b=Book(name="python基础",price=99,author="yuan",pub_date="2017-12-12") b.save() 方式二: Book.objects.create() Book.objects.create(name="老男孩linux",price=78,author="oldboy",pub_date="2016-12-12") 表记录的修改 方式一: b=Book.objects.get(author="oldboy") b.price=120 b.save() 方式二: #update是QuerySet Book.objects.filter(author="yuan").update(price=999) 表记录的删除: Book.objects.filter(author="oldboy").delete() 表记录的查询(重点): book_list = Book.objects.filter(id=2) book_list=Book.objects.exclude(author="yuan").values("name","price") book_list=Book.objects.all() book_list = Book.objects.all()[::2] book_list = Book.objects.all()[::-1] #first,last,get取到的是一个实例对象,并非一个QuerySet的集合对象 book_list = Book.objects.first() book_list = Book.objects.last() book_list = Book.objects.get(id=2)#只能取出一条记录时才不报错 ret1=Book.objects.filter(author="oldboy").values("name") ret2=Book.objects.filter(author="yuan").values_list("name","price") book_list= Book.objects.all().values("name").distinct() book_count= Book.objects.all().values("name").distinct().count() 模糊查询 双下划线__ book_list=Book.objects.filter(name__icontains="P").values_list("name","price") book_list=Book.objects.filter(id__gt=5).values_list("name","price") 多表操作(一对多): #添加记录 #publish_id=2 Book.objects.create(name="linux运维",price=77,pub_date="2017-12-12",publish_id=2) #publish=object Book.objects.create(name="GO",price=23,pub_date="2017-05-12",publish=publish_obj) #查询记录(通过对象) 正向查询: book_obj=Book.objects.get(name="python") pub_obj=book_obj.publish----》书籍对象对应的出版社对象 pub_obj.name 反向查询: pub_obj = Publish.objects.filter(name="人民出版社")[0] pub_obj.book_set.all().values("name","price") #查询记录(filter values 双下划线__) #人民出版社出版过的书籍与价格 ret=Book.objects.filter(publish__name="人民出版社").values("name","price") #python这本书出版社的名字 ret2=Publish.objects.filter(book__name="python").values("name") #python这本书出版社的名字 ret3=Book.objects.filter(name="python").values("publish__name") #北京的出版社出版书的名字 ret4=Book.objects.filter(publish__city="北京").values("name") #2017年上半年出版过书的出版社的名字 ret5=Book.objects.filter(pub_date__lt="2017-07-01",pub_date__gt="2017-01-01").values("publish__name") 多表操作(多对多): 创建多对多的关系 author= models.ManyToManyField("Author")(推荐) 书籍对象它的所有关联作者 obj=book_obj.authors.all() 绑定多对多的关系 obj.add(*QuerySet) obj.remove(author_obj) 如果想向第三张表插入值的方式绑定关系: 手动创建第三张表 # class Book_Author(models.Model): # book=models.ForeignKey("Book") # author=models.ForeignKey("Author") Book_Author.objects.create(book_id=2,author_id=3) 掌握:通过 filter values (双下换线)进行多对多的关联查询(形式和一对多)
models.py
from django.db import models # Create your models here. class Book(models.Model): name=models.CharField(max_length=20) price=models.IntegerField() pub_date=models.DateField() publish=models.ForeignKey("Publish") authors=models.ManyToManyField("Author") def __str__(self): return self.title class Publish(models.Model): name=models.CharField(max_length=32) city=models.CharField(max_length=32) def __str__(self): return self.name class Author(models.Model): name = models.CharField(max_length=32) age = models.IntegerField(default=20) def __str__(self): return self.name
ManyToManyField字段会自动帮我们创建一张表,book_author
Book.objects.create(name='linux',price=68,pub_date='2018-11-18',publish_id='1',authors=2)
将会报错:
Direct assignment to the forward side of a many-to-many set is prohibited. Use authors.set() instead.
我们也可以自己创建第三第三张表,将MangToManyField去掉
from django.db import models # Create your models here. class Book(models.Model): name = models.CharField(max_length=32) price = models.IntegerField() pub_date = models.DateField() publish = models.ForeignKey("Publish",on_delete=models.CASCADE) # authors = models.ManyToManyField("Author") def __str__(self): return self.name class Publish(models.Model): name = models.CharField(max_length=32) city = models.CharField(max_length=32) def __str__(self): return self.name class Author(models.Model): name = models.CharField(max_length=32) age = models.IntegerField() def __str__(self): return self.name class Book_Author(models.Model): book = models.ForeignKey("Book", on_delete=models.CASCADE) author = models.ForeignKey("Author", on_delete=models.CASCADE)
解决TypeError: __init__() missing 1 required positional argument: 'on_delete'
试用Djiango的时候发现执行mange.py makemigrations 和 migrate是会报错,少位置参数on_delete,查了一下是因为指定外键的方式不对,改一下就OK了。
即在外键值的后面加上 on_delete=models.CASCADE
原因: 在django2.0后,定义外键和一对一关系的时候需要加on_delete选项,此参数为了避免两个表里的数据不一致问题,不然会报错: TypeError: __init__() missing 1 required positional argument: 'on_delete' 举例说明: user=models.OneToOneField(User) owner=models.ForeignKey(UserProfile) 需要改成: user=models.OneToOneField(User,on_delete=models.CASCADE) --在老版本这个参数(models.CASCADE)是默认值 owner=models.ForeignKey(UserProfile,on_delete=models.CASCADE) --在老版本这个参数(models.CASCADE)是默认值 参数说明: on_delete有CASCADE、PROTECT、SET_NULL、SET_DEFAULT、SET()五个可选择的值 CASCADE:此值设置,是级联删除。 PROTECT:此值设置,是会报完整性错误。 SET_NULL:此值设置,会把外键设置为null,前提是允许为null。 SET_DEFAULT:此值设置,会把设置为外键的默认值。 SET():此值设置,会调用外面的值,可以是一个函数。 一般情况下使用CASCADE就可以了。
ret1 = Book.objects.filter(authors__name='alex').values('name','price') ret2 = Book.objects.filter(authors__name='alex').values_list('name', 'price') print(ret1) print(ret2) ''' <QuerySet [{'name': 'linux', 'price': 68}, {'name': 'python', 'price': 78}, {'name': 'java', 'price': 88}]> <QuerySet [('linux', 68), ('python', 78), ('java', 88)]> '''
---------->聚合查询和分组查询
<1> aggregate(*args,**kwargs):
通过对QuerySet进行计算,返回一个聚合值的字典。aggregate()中每一个参数都指定一个包含在字典中的返回值。即在查询集上生成聚合。
from django.db.models import Avg,Min,Sum,Max 从整个查询集生成统计值。比如,你想要计算所有在售书的平均价钱。Django的查询语法提供了一种方式描述所有 图书的集合。 >>> Book.objects.all().aggregate(Avg('price')) {'price__avg': 34.35} aggregate()子句的参数描述了我们想要计算的聚合值,在这个例子中,是Book模型中price字段的平均值 aggregate()是QuerySet 的一个终止子句,意思是说,它返回一个包含一些键值对的字典。键的名称是聚合值的 标识符,值是计算出来的聚合值。键的名称是按照字段和聚合函数的名称自动生成出来的。如果你想要为聚合值指定 一个名称,可以向聚合子句提供它: >>> Book.objects.aggregate(average_price=Avg('price')) {'average_price': 34.35} 如果你也想知道所有图书价格的最大值和最小值,可以这样查询: >>> Book.objects.aggregate(Avg('price'), Max('price'), Min('price')) {'price__avg': 34.35, 'price__max': Decimal('81.20'), 'price__min': Decimal('12.99')}
<2> annotate(*args,**kwargs):
可以通过计算查询结果中每一个对象所关联的对象集合,从而得出总计值(也可以是平均值或总和),即为查询集的每一项生成聚合。
查询alex出的书总价格
查询各个作者出的书的总价格,这里就涉及到分组了,分组条件是authors__name
查询各个出版社最便宜的书价是多少
---------->F查询和Q查询
仅仅靠单一的关键字参数查询已经很难满足查询要求。此时Django为我们提供了F和Q查询:
# F 使用查询条件的值,专门取对象中某列值的操作 # from django.db.models import F # models.Tb1.objects.update(num=F('num')+1) # Q 构建搜索条件 from django.db.models import Q #1 Q对象(django.db.models.Q)可以对关键字参数进行封装,从而更好地应用多个查询 q1=models.Book.objects.filter(Q(title__startswith='P')).all() print(q1)#[<Book: Python>, <Book: Perl>] # 2、可以组合使用&,|操作符,当一个操作符是用于两个Q的对象,它产生一个新的Q对象。 Q(title__startswith='P') | Q(title__startswith='J') # 3、Q对象可以用~操作符放在前面表示否定,也可允许否定与不否定形式的组合 Q(title__startswith='P') | ~Q(pub_date__year=2005) # 4、应用范围: # Each lookup function that takes keyword-arguments (e.g. filter(), # exclude(), get()) can also be passed one or more Q objects as # positional (not-named) arguments. If you provide multiple Q object # arguments to a lookup function, the arguments will be “AND”ed # together. For example: Book.objects.get( Q(title__startswith='P'), Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6)) ) #sql: # SELECT * from polls WHERE question LIKE 'P%' # AND (pub_date = '2005-05-02' OR pub_date = '2005-05-06') # import datetime # e=datetime.date(2005,5,6) #2005-05-06 # 5、Q对象可以与关键字参数查询一起使用,不过一定要把Q对象放在关键字参数查询的前面。 # 正确: Book.objects.get( Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6)), title__startswith='P') # 错误: Book.objects.get( question__startswith='P', Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6)))
from django.shortcuts import render,HttpResponse from django.db.models import Avg,Min,Sum,Max,Count from django.db.models import Q,F # Create your views here. from app01.models import * def index(request): return render(request,"index.html") def addbook(request): # Book.objects.create(name="linux运维",price=77,pub_date="2017-12-12",publish_id=2) #publish_obj=Publish.objects.filter(name="人民出版社")[0] #Book.objects.create(name="GO",price=23,pub_date="2017-05-12",publish=publish_obj) # book_obj=Book.objects.get(name="python") # print(book_obj.name) # print(book_obj.pub_date) # # #一对多:book_obj.publish--------一定是一个对象 # print(book_obj.publish.name) # print(book_obj.publish.city) # print(type(book_obj.publish)) #查询人民出版社出过的所有书籍名字和价格 #方式一: # pub_obj=Publish.objects.filter(name="人民出版社")[0] # ret=Book.objects.filter(publish=pub_obj).values("name","price") # print(ret) #方式二 # pub_obj = Publish.objects.filter(name="人民出版社")[0] # print(pub_obj.book_set.all().values("name","price")) #print(type(pub_obj.book_set.all())) #方式三 # ret=Book.objects.filter(publish__name="人民出版社").values("name","price") # print(ret) # # python这本书出版社的名字 # ret2=Publish.objects.filter(book__name="python").values("name") # print(ret2) # ret3=Book.objects.filter(name="python").values("publish__name") # print(ret3) # # ret4=Book.objects.filter(publish__city="北京").values("name") # print(ret4) # # ret5=Book.objects.filter(pub_date__lt="2017-07-01",pub_date__gt="2017-01-01").values("publish__name") # print(ret5) #通过对象的方式绑定关系 # book_obj=Book.objects.get(id=3) # print(book_obj.authors.all()) # print(type(book_obj.authors.all())) # # author_obj=Author.objects.get(id=2) # print(author_obj.book_set.all()) # book_obj=Book.objects.get(id=3) # author_objs=Author.objects.all() # #book_obj.authors.add(*author_objs) # # book_obj.authors.remove(*author_objs) # book_obj.authors.remove(4) # 删除 author id = 4 的那一项 #创建第三张表 # Book_Author.objects.create(book_id=2,author_id=2) # # obj=Book.objects.get(id=2) # print(obj.book_author_set.all()[0].author) # 太麻烦 #alex出过的书籍名称及价格 # ret=Book.objects.filter(book_author__author__name="alex").values("name","price") # 第三张表的查询,太麻烦 # print(ret) # ret2=Book.objects.filter(authors__name="alex").values("name","price","authors__name") # print(ret2) # ret=Book.objects.all().aggregate(Avg("price")) # ret=Book.objects.all().aggregate(Sum("price")) # ret=Book.objects.filter(authors__name="alex").aggregate(alex_money=Sum("price")) # ret=Book.objects.filter(authors__name="alex").aggregate(Count("price")) # print(ret) # ret=Book.objects.values("authors__name").annotate(Sum("price")) # print(ret) # <QuerySet [{'price__sum': 234, 'authors__name': 'alex'}, {'price__sum': 68, 'authors__name': 'xiang'}, # {'price__sum': 98, 'authors__name': 'vincent'}]> # 每个出版社最便宜的书 # ret=Publish.objects.values("name").annotate(abc=Min("book__price")) # ret = Book.objects.values("publish__name").annotate(Min('price')) # print(ret) ''' (0.001) SELECT `app_publish`.`name`, MIN(`app_book`.`price`) AS `book__price__min` FROM `app_publish` LEFT OUTER JOIN `app_book` ON (`app_publish`.`id` = `app_b ook`.`publish_id`) GROUP BY `app_publish`.`name` ORDER BY NULL LIMIT 21; args=() <QuerySet [{'book__price__min': 68, 'name': '南方出版社'}, {'book__price__min': 88, 'name': '机械出版社'}, {'book__price__min': 98, 'name': '人民出版社'}]> ''' # b=Book.objects.get(name="GO",price=77) # print(b) #Book.objects.all().update(price=F("price")+10) # (0.008) UPDATE `app_book` SET `price` = (`app_book`.`price` + 10); args=(10,) # ret=Book.objects.filter(Q(name__contains="G")) # print(ret) # ret=Book.objects.filter(Q(name="GO"),price=87) # print(ret) #ret=Book.objects.filter(price=200) # 若不适宜结果,sql语句不会执行 # for i in ret: # print(i.price) # # Book.objects.all().update(price=200) # ret = Book.objects.filter(price=100) # for i in ret: # print(i.price) # if ret.exists(): # print("ok") # ret=ret.iterator() # print(ret) # # for i in ret: # print(i.name) # # for i in ret: # print(i.name) return HttpResponse("添加成功") def update():pass def delete():pass def select():pass
from django.db import models class Classes(models.Model): """ 班级表,男 """ titile = models.CharField(max_length=32) m = models.ManyToManyField('Teachers',related_name='sssss') class Teachers(models.Model): """ 老师表,女 """ name = models.CharField (max_length=32) class Student(models.Model): """ 学生表 """ username = models.CharField(max_length=32) age = models.IntegerField() gender = models.BooleanField() cs = models.ForeignKey(Classes,related_name='ssss') # cs,cs_id 1 3班 ######################## 单表 ######################## # 增加 # Teachers.objects.create(name='root') # obj = Teachers(name='root') # obj.save() # 查 # Teachers.objects.all() # Teachers.objects.filter(id=1) # Teachers.objects.filter(id=1,name='root') # result = Teachers.objects.filter(id__gt=1) # [obj(id,name),] # result = Teachers.objects.filter(id__gt=1).first() # 删除 # Teachers.objects.filter(id=1).delete() # 改 # Teachers.objects.all().update(name='alex') # Teachers.objects.filter(id=1).update(name='alex') ######################## 一对多 ######################## """ 班级: id name 1 3班 2 6班 学生 id username age gender cs_id 1 东北 18 男 1 2 东北1 118 男 2 2 东北1 118 男 1 """ # 增加 # Student.objects.create(username='东北',age=18,gender='男',cs_id=1) # Student.objects.create(username='东北',age=18,gender='男',cs= Classes.objects.filter(id=1).first() ) # 查看 """ ret = Student.objects.all() # [] # [ obj(..),] # [ obj(1 东北 18 男 1),obj(2 东北1 118 男 2),obj(..),] for item in ret: print(item.id) print(item.username) print(item.age) print(item.gender) print(item.cs_id) print(item.cs.id) print(item.cs.name) """ # 删除 # Student.objects.filter(id=1).delete() # Student.objects.filter(cs_id=1).delete() # cid = input('请输入班级ID') # Student.objects.filter(cs_id=cid).delete() # cname = input('请输入班级名称') # Student.objects.filter(cs_id=cid).delete() # Student.objects.filter(cs__name=cname).delete() ######################## 多对多 ######################## # 多对多 """ 班级: id title 1 3班 2 4班 3 5班 老师: id title 1 Alex 2 老妖 3 瞎驴 4 Eric 老师班级关系表(类): id 班级id 老师id 1 1 2 2 1 3 4 2 2 5 2 3 6 2 4 7 1 5 # 增 obj = Classes.objects.filter(id=1).first() #1 3班 obj.m.add(2) obj.m.add([4,3]) # obj = Classes.objects.filter(id=2).first() #1 3班 # obj.m.add(2) # obj.m.add([4,3]) obj = Classes.objects.filter(id=1).first() #1 3班 # 删除 # obj.m.remove([4,3]) # 清空 obj.m.clear() # 重置 obj.m.set([2,3,5]) # 查第三张表 # 把3班的所有老师列举 obj = Classes.objects.filter(id=1).frist() obj.id obj.titile ret = obj.m.all() # 第三张表 # ret是一个 [ 老师1(id,name),obj(id,name) ] """
from django.db import models 班级: id name 1 3班 2 6班 class School: name = models.CharField(max_length=32) class Classes(models.Model): """ 班级表,男 """ titile = models.CharField(max_length=32) # m = models.ManyToManyField('Teachers') # 多对多 # sch = models.ForeignKey(School) 老师: id title 1 Alex 2 老妖 3 瞎驴 4 Eric class Teachers(models.Model): """ 老师表,女 """ name = models.CharField (max_length=32) 学生 id username age gender cs_id 1 东北 18 男 1 2 东北1 118 男 2 2 东北1 118 男 1 class Student(models.Model): """ 学生表 """ username = models.CharField(max_length=32) age = models.IntegerField() gender = models.BooleanField() cs = models.ForeignKey(Classes) # 示例: - 所有学生的姓名以及其所在班级名称,QuerySet stu_list = Student.objects.all() select * from tb; [obj,obj,obj,obj] stu_list = Student.objects.all().values("id",'username') select id,username from tb; [{"id":1,'username':'xx'},{id:'',username:''}] stu_list = Student.objects.all().values_list("id",'username') [(1,'root'), (2,'alex')] stu_list = Student.objects.all().values('username',"cs__name") for row in stu_list: print(row['username'],row['cs__name']) stu_list = Student.objects.all().values('username',"cs__titile",“cs__fk__name”) - 找到3班的所有学生 Student.objects.filter(cs__name='3班') obj = Classes.objects.filter(name='3班').first() 1. 类代表数据库表 2. 类的对象代指数据库的一行记录 3. FK字段代指关联表中的一行数据(类的对象) 4. - 正向:fk字段 (*****) - 反向:小写类名_set(默认) ==> related_name='ssss' 5. 谁是主表?就全部列出其数据 models.Student.objects.all().values('username', 'cs__titile') models.Classes.objects.all().values('titile', 'ssss__username') 4. M2M字段,自动生成第三张表;依赖关联表对第三张表间接操作 对话框添加,删除,修改: 添加: Ajax偷偷向后台发请求: 1. 下载引入jQuery 2. $.ajax({ url: '/add_classes.html', type: 'POST', data: {'username':'root','password': '123'}, success:function(arg){ // 回调函数,arg是服务端返回的数据 } }) 作业: 1.班级管理(排出老师列) 2.学生管理 添加,删除,修改 3.select标签 val