Django框架ORM之查询函数

 

from django.shortcuts import render,HttpResponse
from book.models import Book
import datetime
# Create your views here.
def add_book(request):

    if request.method == "GET":
        return render(request, "add_book.html")
    else:
        #方式一
        #title =request.POST.get("title")
        #price = request.POST.get("price")
        #pub_date = request.POST.get("pub_date")
        #Book.objects.create(title=title,price=price,pub_date=pub_date)
        #方式二
        #request.POST.dict()
        Book.objects.create(**request.POST.dict())

        return redirect("/book/select")
        #return HttpResponse("添加书籍")


    #添加书籍
    # 方式1
    #date = datetime.date(year=2012,month=12,day=12)
    #book = Book(title="xiyouji", price=199, pub_date=date)
    book = Book(title="xiyouji",price=199,pub_date="2012-12-12")
    print(book.id) #None
    book.save() #执行sql
    print(book.id) # 3

    # 方式2
    book = Book.objects.create(title="sanguoyanyi",price=299,pub_date="2011-11-11")
    print(book.id)
    print(book.price)

def select_book(request):

    #return render(request,"add_book.html")
    # (1) 查询所有的书籍，返回值是一个queryset类型对象
    #book_list= Book.objects.all()
    '''
    ORM数据引擎：
    
    select id, title, price, pub_date from book:
    +------+--------------+---------+------------+
    id  title             price     pub_date
    +------+--------------+---------+------------+
    1    西游记            499.00     2011-12-12
    2    三国演义          399.00     2019-06-12
    3    水浒传            299.00     2008-06-12
    4    红楼梦            199.00     2020-06-12
    +------+--------------+---------+------------+
    book01 = Book(1 | 西游记  |499.00 |2011-12-12)
    book02 = Book(2 | 三国演义  |399.00  |2019-06-12)
    book03 = Book(3 | 水浒传    |299.00  |2008-06-12)
    book04 = Book(4 | 红楼梦    |199.00  |2020-06-12)
    
    book_list = queryset[book01,book02,book03,book04]    
    
    '''
    #print ("book_list",book_list) # <QuerySet [<Book: Book object (1)>,...]

    #QuerySet:支持索引操作，支持遍历
    #book = book_list[0]
    #print(book.id) # 1
    #print(book.title) # 西游记
    #print(book.price) # 499.00
    # print(book_list.title)
    #for book in book_list:
        #print (book.id,book.title)  #1 西游记 2 三国演义 3 水浒传 4 红楼梦

    #return HttpResponse("添加书籍")

    # (2) filter方法： 返回queryset
    book_list = Book.objects.filter(price=455) #查看价格为455.00的书籍信息

    # (3) exclude方法：排除符合条件的返回queryset类型对象
    book_list = Book.objects.exclude(price=455) #排除价格等于455.00的书籍信息

    # (4) get方法： 返回值模型类对象 特点： 查询有且只有一个对象时正常返回
    book = Book.objects.get(id=7) #查看id为7的书籍信息(唯一一条)
    print("book",book)
    print("book", book.title,book.price) ##查看id为7的书籍信息的书籍名称和价格(唯一一条)

    # (5) first方法，last方法
    book = Book.objects.first() # 查询第一条书籍信息
    book = Book.objects.last() # 查询最后一条书籍信息
    print(book.title)

    # (6) queryset.orderby方法：
    book_list = Book.objects.all().order_by("-price") # 按价格排除
    book_list = Book.objects.all().filter(price_gt=300).order_by("-price") #查询价格大于300.00，并排序

    # (7) queryset.count() 计数：
    n = book = Book.objects.count()
    print (n) # 9

    # (8) value(列表.字典)，value_list(列表.元组)
    #value(列表.字典)
    book_list = Book.objects.values("title","price","pub_date")
    book_list = Book.objects.filter(price=455).values("title","price","pub_date")
    print("book_list", book_list)
    #value_list(列表.元组)
    book_list2 = Book.objects.filter(price=455).values("title","price","pub_date")
    print("book_list2", book_list2)


    return render(request,"books.html",{"book_list":book_list})