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$ne
$ne聚合运算符比较两个值，true如果两个值不相等，则返回，否则返回false。
参数
-
expression1：要比较的第一个值。
-
expression2: 第二个要比较的值。
示例（MongoDB 外壳）
以下示例演示如何使用$ne运算符来识别状态发生变化的订单。
创建示例文档
db.orders.insertMany([
{ _id: 1, orderId: "A123", status: "shipped", expectedStatus: "shipped" },
{ _id: 2, orderId: "B456", status: "pending", expectedStatus: "shipped" },
{ _id: 3, orderId: "C789", status: "delivered", expectedStatus: "delivered" }
]);
查询示例
db.orders.aggregate([
{
$project: {
orderId: 1,
status: 1,
expectedStatus: 1,
needsAttention: { $ne: ["$status", "$expectedStatus"] }
}
}
]);
输出
[
{ _id: 1, orderId: 'A123', status: 'shipped', expectedStatus: 'shipped', needsAttention: false },
{ _id: 2, orderId: 'B456', status: 'pending', expectedStatus: 'shipped', needsAttention: true },
{ _id: 3, orderId: 'C789', status: 'delivered', expectedStatus: 'delivered', needsAttention: false }
]
代码示例
要查看使用$ne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('orders');
const result = await collection.aggregate([
{
$project: {
orderId: 1,
status: 1,
expectedStatus: 1,
needsAttention: { $ne: ["$status", "$expectedStatus"] }
}
}
]).toArray();
console.log(result);
await client.close();
}
example();
- Python
-
from pymongo import MongoClient
def example():
client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
db = client['test']
collection = db['orders']
result = list(collection.aggregate([
{
'$project': {
'orderId': 1,
'status': 1,
'expectedStatus': 1,
'needsAttention': { '$ne': ['$status', '$expectedStatus'] }
}
}
]))
print(result)
client.close()
example()
