Django基础6

上山打老虎

1.模板的继承(使用频率较高)
　　需求: 页面主体不变 部分区域变化
模板继承　　1.需要现在母版中使用block提前划定区域

{% block 区域名称 %}
    {% endblock %}

　　2.在子版中先继承再局部替换

{% extends '母版.html' %}
    {% block 区域名称 %}
    {% endblock %}

　　总结
　　母版一般情况下都应该至少含有三个区域

1.css区域
    2.content区域
    3.js区域

　　补充
    {{ block.super }}  调用母版内容
2.模板的导入(了解)

　　{% include 'myform.html' %}

3.数据库正向与反向迁移

　　正向迁移(将django中的类导入到MySQL中变成表)

python3 manage.py makemigrations
  python3 manage.py migrate

　　反向迁移
　　inspectdb

4.单表查询预备知识

from django.db import models

# Create your models here.
class Books(models.Model):
  title = models.CharField(max_length=32)
  price = models.DecimalField(max_digits=8,decimal_places=2)
  # 日期类型
  publish_time = models.DateField(auto_now_add=True)
  """
  auto_now:每次修改数据之后都会自动更新当前时间
  auto_now_add:第一次创建数据的时候自动记录时间
  """
  # publish_time = models.DateTimeField()
  def __str__(self):
    return self.title  # 只能返回字符串类型的数据


class Book(models.Model):
  title = models.CharField(max_length=32)
  price = models.DecimalField(max_digits=8, decimal_places=2)
  # 日期类型
  publish_time = models.DateField(auto_now_add=True)
  publish = models.ForeignKey(to='Publish')
  authors = models.ManyToManyField(to='Author')
  def __str__(self):
    return self.title  # 只能返回字符串类型的数据


class Publish(models.Model):
  title = models.CharField(max_length=32)
  addr = models.CharField(max_length=64)
  def __str__(self):
    return self.title


class Author(models.Model):
  name = models.CharField(max_length=32)
  age = models.IntegerField()
  author_detail = models.OneToOneField(to='AuthorDetail')
  def __str__(self):
    return self.name


class AuthorDetail(models.Model):
  phone = models.BigIntegerField()
  addr = models.CharField(max_length=64)
  def __str__(self):
    return self.addr

　　
5.django脚本环境


　　django默认情况下是不允许单独使用某个功能部分(models.py)
　　解决方法：

1.要么自己新建一个py文件
2.要么使用自带的tests文件
      import os
      if __name__ == "__main__":
          os.environ.setdefault("DJANGO_SETTINGS_MODULE", "day47.settings")
          import django
          django.setup()

　　
6.单表查询关键字

# 增   1.create()
  # models.Books.objects.create(title='三国演义',price=456.23)
  # models.Books.objects.create(title='水浒传',price=876.45)
  # models.Books.objects.create(title='聊斋志异',price=123.69)
  # models.Books.objects.create(title='草堂笔记',price=456.96)

  # 查   2.all()
  # res = models.Books.objects.all()
  # print(res)  # QuerySet对象
  # print(res.query)  # 只要是QuerySet对象就可以点query查看内部SQL语句

  # 查   3.filter()
  # res1 = models.Books.objects.filter()  # pk特指当前表的主键字段
  # print(res1)  # QuerySet对象
  # print(res1.query)
  # print(res1.first())  # 获取列表中第一个数据对象
  # print(res1.last())  # 获取列表中最后一个数据对象

  # 4.values与5.values_list
  # res2 = models.Books.objects.values('title','price')
  # print(res2)  # QuerySet对象   可以看成列表套字典
  # print(res2.query)

  # res3 = models.Books.objects.values_list('title','price')
  # print(res3)  # QuerySet对象   可以看成列表套元祖
  # print(res3.query)

  # 6.查 get()   不推荐使用
  # res4 = models.Books.objects.get(pk=1)
  # print(res4)  # 数据对象
  # res5 = models.Books.objects.get(pk=100)
  # print(res5)  # 数据对象
  # res6 = models.Books.objects.filter(pk=100)
  # print(res6)  # 数据对象

  # 7.取反  exclude()
  # res7 = models.Books.objects.exclude(pk=1)
  # print(res7)  # QuerySet
  # print(res7.query)


  # 8.排序   order_by()    默认是升序(asc)  字段前面加负号降序(desc)
  # res8 = models.Books.objects.order_by('price')
  # res8 = models.Books.objects.order_by('-price')
  # select * from books order by price desc,price asc;
  # res8 = models.Books.objects.order_by('-price','price')
  # print(res8)  # QuerySet对象
  # print(res8.query)


  # 9.反转  reverse()     必须先有顺序才可以反转
  # res9 = models.Books.objects.all()
  # res9 = models.Books.objects.order_by('price').reverse()
  # print(res9)

  # 10.去重 distinct()
  # res10 = models.Books.objects.all().distinct()
  # res10 = models.Books.objects.values('title','price').distinct()
  # print(res10)

  # 11.计数 count()
  # res11 = models.Books.objects.count()
  # print(res11)  # 6

  # 12.判断是否有数据   exists()
  # res12 = models.Books.objects.filter(pk=999).exists()
  # print(res12)  # False

  # 13.update()
  # 14.delete()

7.单表查询之神奇的双下划线

# 查询筛选价格的书籍
  # res = models.Books.objects.filter(price__gt=200)
  # print(res)
  # res1 = models.Books.objects.filter(price__lt=200)
  # print(res1)
  # res2 = models.Books.objects.filter(price__gte=456.23)
  # print(res2)
  # res3 = models.Books.objects.filter(price__lte=456.23)
  # print(res3)

  # 成员运算
  # res4 = models.Books.objects.filter(price__in=(456.23,111))
  # print(res4)
  # 范围查询
  # res5 = models.Books.objects.filter(price__range=(100,456.23))
  # print(res5)
  # 模糊查询
  # 查询书籍名称中含有字母a的书
  # res6 = models.Books.objects.filter(title__contains='a')
  # print(res6)  # 区分
  # res7 = models.Books.objects.filter(title__icontains='a')
  # print(res7)  # 忽略大小写

  # 日期相关
  # 查看出版月份是五月的书
  # res8 = models.Books.objects.filter(publish_time__month=5)
  # print(res8)
  # print(res8.query)
  # res9 = models.Books.objects.filter(publish_time__year=2021)
  # print(res9)

8.多表查询之外键字段增删改查

# 增
  # models.Book.objects.create(title='三国演义',price=345.43,publish_id=1)
  # models.Book.objects.create(title='红楼梦',price=678.31,publish_id=2)

  # publish_obj = models.Publish.objects.filter(pk=2).first()
  # models.Book.objects.create(title='三国演义',price=345.43,publish=publish_obj)
  # models.Book.objects.create(title='七龙珠',price=908.43,publish=publish_obj)

  # 改
  # models.Book.objects.filter(pk=2).update(publish_id=1)
  # models.Book.objects.filter(pk=2).update(publish=publish_obj)

  # 删 级联更新级联删除
  # models.Publish.objects.filter(pk=1).delete()


  # 多对多
  book_obj = models.Book.objects.filter(pk=3).first()
  # 绑定关系
  # book_obj.authors.add(1)  # 去书与作者的关系表中绑定关系
  # book_obj.authors.add(1,2)  # 去书与作者的关系表中绑定关系
  # book_obj.authors.add(author_obj1)
  # book_obj.authors.add(author_obj1,author_obj2)

  # 修改关系
  # book_obj.authors.set([1,])
  # book_obj.authors.set([1,2])
  # book_obj.authors.set([author_obj,])
  # book_obj.authors.set([author_obj1,author_obj2])

  # 移除关系
  # book_obj.authors.remove(1)
  # book_obj.authors.remove(1,2)
  # book_obj.authors.remove(author_obj,)
  # book_obj.authors.remove(author_obj1,author_obj2)

  # 清空关系
  book_obj.authors.clear()