本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。
$unset
8.0 版的新功能
Elastic 叢集不支援。
Amazon DocumentDB 中的$unset彙總階段可讓您從文件中移除欄位。
參數
範例 (MongoDB Shell)
下列範例示範如何使用$unset彙總階段來移除 price 欄位。
建立範例文件
db.inventory.insertMany([
{ item: "pencil", quantity: 100, price: 0.24},
{ item: "pen", quantity: 204, price: 1.78 }
]);
彙總範例
db.inventory.aggregate([
{
$unset: "price"
}
])
輸出
[
{
_id: ObjectId('69248951d66dcae121d2950d'),
item: 'pencil',
quantity: 100
},
{
_id: ObjectId('69248951d66dcae121d2950e'),
item: 'pen',
quantity: 204
}
]
程式碼範例
若要檢視使用 $unset命令的程式碼範例，請選擇您要使用的語言標籤：
- 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 inventory = db.collection('inventory');
const result = await inventory.aggregate([
{
$unset: "price"
}
]).toArray();
console.log(result);
client.close();
}
example();
- Python
-
from pymongo import MongoClient
def example():
client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
db = client['test']
inventory = db['inventory']
result = list(inventory.aggregate([
{
"$unset": "price"
}
]))
print(result)
client.close()
example()
