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$trim
4.0 版的新增内容
Amazon DocumentDB 中的$trim运算符用于从字符串中删除前导 and/or 尾随的空格字符。
参数
示例（MongoDB 外壳）
以下示例演示如何使用$trim运算符从字符串中删除前导和尾随空格。
创建示例文档
db.people.insertMany([
{ "name": " John Doe " },
{ "name": " Bob Johnson " }
])
查询示例
db.people.aggregate([
{ $project: {
"name": { $trim: {input: "$name"}}
}}
])
输出
[
{ "name": "John Doe" },
{ "name": "Bob Johnson" }
]
代码示例
要查看使用该$trim命令的代码示例，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('people');
const result = await collection.aggregate([
{ $project: {
"name": { $trim: {input: "$name" }}
}}
]).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']
collection = db['people']
result = list(collection.aggregate([
{"$project": {
"name": {"$trim": {"input": "$name"}}
}}
]))
print(result)
client.close()
example()
