MongoEngine - 排序

QuerySet 的 order_by() 函数用于以已排序的方式获取查询结果。使用方法如下 -

Qset.order_by(‘fieldname’)

默认情况下，排序顺序为升序。对于降序，请在字段名称后面添加 - 符号。例如，要以升序获取按价格排序的列表 -

from mongoengine import *
con=connect('newdb')

class products (Document):
   ProductID=IntField(required=True)
   company=StringField()
   Name=StringField()
   price=IntField()
for product in products.objects.order_by('price'):
   print ("Name:{} company:{} price:{}".format(product.Name, product.company, product.price))

输出

Name:Router company:Iball price:2000
Name:Scanner company:Cannon price:5000
Name:Printer company:Cannon price:12500
Name:Laptop company:Acer price:25000
Name:TV company:Philips price:31000
Name:Laptop company:Dell price:45000
Name:TV company:Samsung price:50000

以下代码将按姓名降序获取列表 -

for product in products.objects.order_by('-Name'):
   print ("Name:{} company:{} price:{}".format(product.Name, product.company, product.price))

输出

Name:TV company:Samsung price:50000
Name:TV company:Philips price:31000
Name:Scanner company:Cannon price:5000
Name:Router company:Iball price:2000
Name:Printer company:Cannon price:12500
Name:Laptop company:Acer price:25000
Name:Laptop company:Dell price:45000

你还可以对多个字段进行排序。此代码将按公司、价格列表升序获取结果。

for product in products.objects.order_by('company','price'):
   print ("Name:{} company:{} price:{}".format(product.Name, product.company, product.price))

输出

Name:Laptop company:Acer price:25000
Name:Scanner company:Cannon price:5000
Name:Printer company:Cannon price:12500
Name:Laptop company:Dell price:45000
Name:Router company:Iball price:2000
Name:TV company:Philips price:31000
Name:TV company:Samsung price:50000