Mongodb 在一次往返中执行多个查询

使用Mongodb进行一次往返中执行多个查询是一种高效的数据库操作方式。通过这种方式，我们可以在一次网络往返中完成多个查询操作，减少了网络延迟的影响，提高了查询的效率。下面我们将介绍如何使用Mongodb进行一次往返中执行多个查询，并提供一个案例代码。

db.orders.aggregate([
  { $match: { userId: "123456" } },
  { $lookup: {
     from: "products",
     localField: "productId",
     foreignField: "_id",
     as: "product"
  }},
  { $unwind: "$product" },
  { $project: { userId: 1, orderId: 1, productName: "$product.name", price: "$product.price" }}
])

db.products.find({ category: "electronics" })

python
from pymongo import MongoClient
def execute_multiple_queries():
    client = MongoClient("mongodb://localhost:27017/")
    db = client["mydatabase"]
    
    orders = db.orders.aggregate([
      { $match: { userId: "123456" } },
      { $lookup: {
         from: "products",
         localField: "productId",
         foreignField: "_id",
         as: "product"
      }},
      { $unwind: "$product" },
      { $project: { userId: 1, orderId: 1, productName: "$product.name", price: "$product.price" }}
    ])
    
    products = db.products.find({ category: "electronics" })
    
    return orders, products