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。
$pull
$pull 運算子用於從陣列中移除符合指定條件之值的所有執行個體。當您需要從文件中的陣列欄位中移除特定元素時，此運算子非常有用。
參數
範例 (MongoDB Shell)
下列範例示範如何使用 $pull運算子從陣列欄位移除元素。
建立範例文件
db.restaurants.insertMany([
{
name: "Pizza Hut",
cuisine: "Italian",
features: ["Delivery", "Takeout", "Dine-in"]
},
{
name: "Sushi Saito",
cuisine: "Japanese",
features: ["Dine-in", "Private Dining"]
},
{
name: "Taco Bell",
cuisine: "Mexican",
features: ["Delivery", "Takeout", "Drive-thru"]
}
])
查詢範例
db.restaurants.updateMany(
{ cuisine: "Italian" },
{ $pull: { features: "Takeout" } }
)
輸出
{
"acknowledged" : true,
"matchedCount" : 1,
"modifiedCount" : 1
}
上述查詢會從cuisine欄位為「義大利文」的所有文件中移除「擷取」功能。
程式碼範例
若要檢視使用 $pull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 updateRestaurants() {
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 restaurants = db.collection('restaurants');
await restaurants.updateMany(
{ cuisine: 'Italian' },
{ $pull: { features: 'Takeout' } }
);
const updatedRestaurants = await restaurants.find({}).toArray();
console.log(updatedRestaurants);
await client.close();
}
updateRestaurants();
- Python
-
from pymongo import MongoClient
def update_restaurants():
client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
db = client.test
restaurants = db.restaurants
result = restaurants.update_many(
{ 'cuisine': 'Italian' },
{ '$pull': { 'features': 'Takeout' } }
)
updated_restaurants = list(restaurants.find({}))
print(updated_restaurants)
client.close()
update_restaurants()
