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$push
$push聚合运算符为每个组返回一个包含指定表达式中所有值的数组。它通常在$group舞台中用于将值累积到数组中。
参数
示例（MongoDB 外壳）
以下示例演示如何使用$push运算符收集每个类别的所有产品名称。
创建示例文档
db.sales.insertMany([
{ _id: 1, category: "Electronics", product: "Laptop", amount: 1200 },
{ _id: 2, category: "Electronics", product: "Mouse", amount: 25 },
{ _id: 3, category: "Furniture", product: "Desk", amount: 350 },
{ _id: 4, category: "Furniture", product: "Chair", amount: 150 },
{ _id: 5, category: "Electronics", product: "Keyboard", amount: 75 }
]);
查询示例
db.sales.aggregate([
{
$group: {
_id: "$category",
products: { $push: "$product" }
}
}
]);
输出
[
{ _id: 'Furniture', products: [ 'Desk', 'Chair' ] },
{ _id: 'Electronics', products: [ 'Laptop', 'Mouse', 'Keyboard' ] }
]
代码示例
要查看使用$push聚合运算符的代码示例，请选择要使用的语言的选项卡：
- Node.js
-
const { MongoClient } = require('mongodb');
async function example() {
const client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
const db = client.db('test');
const collection = db.collection('sales');
const result = await collection.aggregate([
{
$group: {
_id: "$category",
products: { $push: "$product" }
}
}
]).toArray();
console.log(result);
await client.close();
}
example();
- Python
-
from pymongo import MongoClient
def example():
client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
db = client['test']
collection = db['sales']
result = list(collection.aggregate([
{
'$group': {
'_id': '$category',
'products': { '$push': '$product' }
}
}
]))
print(result)
client.close()
example()
