ORM 之单表查询案例

ORM单表查询

from django.shortcuts import render,HttpResponse
from app1.models import Book
# Create your views here.
def select(request):
	# 1.all 查询所有数据
	data = Book.objects.all()
	print(data)

	# 2.count 获取数据总数 select count(*) from book
	res = data.count()
	print(res)

	# 3.first: 返回的第一条数据对象
	res = data.first()
	print(res)
	print(res.id,res.title)

	# 4.last: 返回的最后一个数据对象
	res = data.last()
	print(res.id)

	# 5.order_by 排序(正序)  order by id asc
	data = Book.objects.order_by('id')
	print(data)

	# 6.order_by 排序(倒序) reverse  order by id desc 推荐;
	data = Book.objects.order_by('id').reverse()
	print(data)

	# 扩展写法 [可以在排序的字段前面加上-,表达倒序] 不推荐;
	data = Book.objects.order_by('-id')
	print(data)

	# 7.filter 按条件查询[相当于where] 返回的queryset对象
	data = Book.objects.filter(price=81).order_by("-id")
	# select * from book where price=81 order by id desc
	for i in data.order_by("-id"):
		print(i.id)
	print(data[0].id,"<=====>")

	# 8.exists():  如果QuerySet包含数据，就返回True，否则返回False
	data = Book.objects.filter(id=10)
	res = data.exists()
	print(res)

	# 9.get 返回一个模型类对象 [等价于表对象]
	# data = Book.objects.get(id=100000) # error 找不到或者找到多条数据都会报错;
	# print(data)

	# 10.exclude: 排除符合条件的对象,返回的依然是queryset对象 [表达不等于,除了的概念]
	data = Book.objects.exclude(id=10) # select * from book where id != 10
	print(data)

	# 11.values 查找某个字段值,返回字典
	data = Book.objects.filter(price=78).values("id","title")
	print(data)

	# 12.values_list 查找某个字段值,返回元组
	data = Book.objects.filter(price=78).values_list("id","title")
	print(data)

	# 13.distinct 去重 select distinct(price) from app1_book
	data = Book.objects.all().values("price").distinct()
	print(data)

	# 链式操作(连贯操作)
	# select "id","title" from book where price = 78 order by id desc
	data = Book.objects.filter(price=78).values("id","title").order_by("id").reverse()
	print(data)
	return HttpResponse("select ok")

def select2(request):
	# 范围查询
	# in  => __in
	# select * from book where price in (78,79,90)
	data = Book.objects.filter(price__in=[78,79,90])
	print(data,1)

	# >   => __gt
	# select * from book where price > 79
	data = Book.objects.filter(price__gt=79)
	print(data,2)

	# >=  => __gte
	# select * from book where price >= 79
	data = Book.objects.filter(price__gte=79)
	print(data,3)

	# <   => __lt
	# select * from book where price < 79
	data = Book.objects.filter(price__lt=79)
	print(data,4)

	# <=  => __lte
	data = Book.objects.filter(price__lte=79)
	print(data,5)

	# between .. and .. =>  __range=[100,200]
	# select * from book where price between 100 and 200;
	data = Book.objects.filter(price__range=[100,200])
	print(data,6)


	# like模糊查询
	# __contains="金"
	# like => __contains="金"
	#  select * from book where title like "%瓶%";
	data = Book.objects.filter(title__contains="瓶")
	print(data,7)


	# like(忽略大小写)
	# __icontains="a"
	data = Book.objects.filter(title__icontains="ab")
	print(data,8)

	# __startswith="aa" 以..开头
	data = Book.objects.filter(title__startswith="三")
	print(data,9)

	# __endswith="bb"   以..结尾
	data = Book.objects.filter(title__endswith="5")
	print(data,10)


	# 针对于date类型
	data = Book.objects.filter(id=10).values("pub_date")
	print(data[0]["pub_date"],11)

	# select * from book where year(pub_date) = 2021
	data = Book.objects.filter(pub_date__year = 2021 )
	data = Book.objects.filter(pub_date__month=12)
	data = Book.objects.filter(pub_date__day=14)
	print(data , 12)
	# __year  过滤日期字段的年份
	# __month 过滤日期字段的月份
	# __day   过滤日期字段的日

	# 扩展 正则匹配 mysql可以使用正则 但是不好事,效率低,查询速度低下,不建议使用;了解
	data = Book.objects.filter(title__regex="^金.*$")
	# print(data,11)
	return HttpResponse("select2 ok")