MongoEngine - 排序

QuerySet 的 order_by() 函式用於以已排序的方式獲取查詢結果。使用方法如下 -

Qset.order_by(‘fieldname’)

預設情況下，排序順序為升序。對於降序，請在欄位名稱後面新增 - 符號。例如，要以升序獲取按價格排序的列表 -

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))

輸出

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

以下程式碼將按姓名降序獲取列表 -

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

輸出

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

你還可以對多個欄位進行排序。此程式碼將按公司、價格列表升序獲取結果。

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

輸出

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