10.4ORM回顾!

2018-10-4 17:41:52

继续优化一下我的博客项目!!

贴上orm参考连接:https://www.cnblogs.com/yuanchenqi/articles/8963244.html

回顾ORM

其实就两种数据方式!

1. 基于对象的

就是通过对象来查找属性

# 正向查询按字段：　　

# 反向查询按     表名小写_set.all()

2. 基于query的

# 正向查询：按字段  反向查询：表名小写

方式实例:
　　models 类:

from django.db import models

# Create your models here.
from django.db import models

# Create your models here.

class Author(models.Model):
    nid = models.AutoField(primary_key=True)
    name=models.CharField( max_length=32)
    age=models.IntegerField()

    # 与AuthorDetail建立一对一的关系
    authorDetail=models.OneToOneField(to="AuthorDetail",on_delete=models.CASCADE)

class AuthorDetail(models.Model):

    nid = models.AutoField(primary_key=True)
    birthday=models.DateField()
    telephone=models.BigIntegerField()
    addr=models.CharField( max_length=64)

class Publish(models.Model):
    nid = models.AutoField(primary_key=True)
    name=models.CharField( max_length=32)
    city=models.CharField( max_length=32)
    email=models.EmailField()

class Book(models.Model):

    nid = models.AutoField(primary_key=True)
    title = models.CharField( max_length=32)
    publishDate=models.DateField()
    price=models.DecimalField(max_digits=5,decimal_places=2)

    # 与Publish建立一对多的关系,外键字段建立在多的一方
    publish=models.ForeignKey(to="Publish",to_field="nid",on_delete=models.CASCADE)
    # 与Author表建立多对多的关系,ManyToManyField可以建在两个模型中的任意一个，自动创建第三张表
    authors=models.ManyToManyField(to='Author',)

放上 orm查询的类!有详细注释

from django.shortcuts import render,HttpResponse

# Create your views here.

from app01 import models

def query(request):

    # #####################基于对象查询(子查询)##############################
    #                按字段（publish）
    # 一对多   book  ----------------->  publish
    #               <----------------
    #                 book_set.all()

    # 正向查询按字段：

    # 查询python这本书籍的出版社的邮箱

    # python=models.Book.objects.filter(title="python").first()
    # print(python.publish.email)

    # 反向查询按     表名小写_set.all()

    # 苹果出版社出版的书籍名称

    # publish_obj=models.Publish.objects.filter(name="苹果出版社").first()
    # for obj in publish_obj.book_set.all():
    #     print(obj.title)

    #                按字段（authors.all()）
    # 多对多   book  ----------------------->  author
    #               <----------------
    #                  book_set.all()

    # 查询python作者的年龄
    # python = models.Book.objects.filter(title="python").first()
    # for author in python.authors.all():
    #     print(author.name ,author.age)

    # 查询alex出版过的书籍名称

    # alex=models.Author.objects.filter(name="alex").first()
    # for book in alex.book_set.all():
    #     print(book.title)

    #                  按字段 authorDetail
    # 一对一   author  ----------------------->  authordetail
    #                <----------------
    #                  按表名  author

    # 查询alex的手机号
    # alex=models.Author.objects.filter(name='alex').first()
    # print(alex.authorDetail.telephone)

    # 查询家在山东的作者名字

    # ad_list=models.AuthorDetail.objects.filter(addr="shandong")
    #
    # for ad in ad_list:
    #     print(ad.author.name)

    '''
    对应sql:

       select publish_id from Book where title="python"    # 查询的nid = 1
       select email from Publish where nid =   1

    '''

    # #####################基于queryset和__查询（join查询）############################

    # 正向查询：按字段  反向查询：表名小写

    # 查询python这本书籍的出版社的邮箱
    # ret=models.Book.objects.filter(title="python").values("publish__email")
    # print(ret.query)  # 打印这条query的sql语句

    '''
    select publish.email from Book
    left join Publish on book.publish_id=publish.nid
    where book.title="python"
    '''

    # 苹果出版社出版的书籍名称
    # 方式1：
    ret1=models.Publish.objects.filter(name="苹果出版社").values("book__title")
    print("111111111====>",ret1.query)
    #方式2：
    ret2=models.Book.objects.filter(publish__name="苹果出版社").values("title")
    print("2222222222====>", ret2.query)

    #查询alex的手机号
    # 方式1：
    ret=models.Author.objects.filter(name="alex").values("authorDetail__telephone")

    # 方式2：
    models.AuthorDetail.objects.filter(author__name="alex").values("telephone")

    # 查询手机号以151开头的作者出版过的书籍名称以及书籍对应的出版社名称
    # filter就是join on 操作 添加表
    # 不要管sql语句和表多少,只要join好表 数据字段都可以直接values
    #  先有个基表 书,  然后最终要查手机号, 然后反向推出来需要的表,然后正向连表就好了
    ret=models.Book.objects.filter(authors__authorDetail__telephone__startswith="").values('title', "publish__name")
    print(ret.query)

    return HttpResponse("OK")

query的查询  只要连过的表就可以随意拿数据,  正向就用字段,反向就用表名小写! 注释很清楚

贴上笔记!

day81

sql:

  单表处理：
  Book

   id title  price    publish       email      addr
   1  python  100    苹果出版社   123@qq.com   北京
   2  go      200    橘子出版社   234@qq.com   南京
   3  java    211    橘子出版社   234@qq.com   南京
   4  linux   22     橘子出版社   234@qq.com   南京   

   ###################一对多######################多表：

   Book

   id title    price     publish_id
   1  python    100         1
   2  go        200         2
   3  java      211         2
   4  linux     22          2   

  Publish

   id      name        email        addr
   1     苹果出版社   123@qq.com   北京
   2     橘子出版社   234@qq.com   南京

   结论: 一旦确定表关系是一对多，那么关联字段建在多的表中

   book:

   Foreignkey   publish_id  refference Publish(id)

   #######################多对多#################################

   Book

   id title    price     publish_id
   1  python    100         1
   2  go        200         2
   3  java      211         2
   4  linux     22          2   

    Author

    id   name  age
    1    alex   38
    2    liwen  43

    Author_Book

    id   author_id    book_id
    1       1            1
    2       1            2
    3       2            2

    结论；一旦是多对多的关系：需要建立第三张关系表

    #######################一对一#################################

    Author

    id   name  age
    1    alex   38
    2    liwen  43    

    AuthorDetail     

    id   tel     gf     author_id(unique)
    1    131    钢蛋        1
    2    121    铁锤        2

SELECT
"app01_book"."title" FROM "app01_publish"
LEFT OUTER JOIN "app01_book" ON ("app01_publish"."nid" = "app01_book"."publish_id")
 WHERE "app01_publish"."name" = 苹果出版社

SELECT
"app01_book"."title" FROM "app01_book" INNER JOIN
"app01_publish" ON ("app01_book"."publish_id" = "app01_publish"."nid")
WHERE "app01_publish"."name" = 苹果出版社

SELECT

"app01_book"."title", "app01_publish"."name"
 FROM "app01_book" INNER JOIN
 "app01_book_authors" ON ("app01_book"."nid" = "app01_book_authors"."book_id")
 INNER JOIN "app01_author" ON ("app01_book_authors"."author_id" = "app01_author"."nid") INNER JOIN "app01_authordetail" ON ("app01_author"."authorDetail_id" = "app01_authordetail"."nid")
 INNER JOIN "app01_publish" ON ("app01_book"."publish_id" = "app01_publish"."nid") 

 WHERE "app01_authordetail"."telephone" LIKE 151% ESCAPE '\'