MongoDB基本增删改查操作-基于Node.JS驱动-蒲公英云

本文基于MongoDB的Node.JS驱动实现MongoDB基本的增删改查操作。驱动官方文档见：mongodb.github.io/node-mongod…。

1 插入文档

MongoDB中Collection类的insertOne和insertMany方法用来插入文档。

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
// Connection URl
const url = 'mongodb://localhost:27017';
// Database name
const dbName = 'myproject';
const client = new MongoClient(url);
(async function() {
    try {
        await client.connect();
        console.log('connected correctly to server');
        const db = client.db(dbName);
        // Insert a single document
        let r = await db.collection('inserts').insertOne({
    a: 1});
        assert.equal(1, r.insertedCount);
        // Insert multiple documents
        r = await db.collection('inserts').insertMany([{
    a: 2}, {
    a: 3}]);
        assert.equal(2, r.insertedCount);
        // Close connection
        client.close();
    } catch(err) {
        console.log(err.stack);
    }
})();
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第一个insert语句向inserts集合中插入单个文档，注意在MongoDB中无需显示的创建集合inserts，MongoDB服务会在首次插入文档时自动创建该集合。 insertOne和insertMany方法接收第二个参数options，可以配置写关注、函数序列化等参数，具体参数列表见：mongodb.github.io/node-mongod…。例如下面这段代码会将传入的函数序列化并写入到副本集replica set：

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
// Connection URL
const url = 'mongodb://localhost:27017';
// Database name
const dbName = 'myproject';
const client = new MongoClient(url);
(async function() {
    try {
        await client.connect();
        console.log('connected correctly to server');
        const db = client.db(dbName);
        // Insert a single document
        const r = await db.collection('inserts').insertOne({
            a: 1,
            b: function () {
    return 'hello';} 
        }, {
            w: 'majority',
            wtimeout: 10000,
            serializeFunctions: true,
            forceServerObjectId: true
        });
        assert.equal(1, r.insertedCount);
        client.close();
    } catch(err) {
        console.log(err.stack);
    }
})();
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2 更新文档

Collection类的updateOne和updateMany方法用于实现更新操作。

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
// Connection URL
const url = 'mongodb://localhost:27017';
// Database name
const dbName = 'myproject';
const client = new MongoClient(url);
(async function () {
    try {
        await client.connect();
        console.log("Connected correctly to server");
        const db = client.db(dbName);
        // Get the updates collection
        const col = db.collection('updates');
        // Insert some documents
        let r = await col.insertMany([{
    a: 1}, {
    a: 2}, {
    a: 2}]);
        assert.equal(3, r.insertedCount);
        // Update a single document
        r = await col.updateOne({
    a: 1}, {
    $set: {
    b: 1}});
        assert.equal(1, r.matchedCount);
        assert.equal(1, r.modifiedCount);
        // Update multiple documents
        r = await col.updateMany({
    a: 2}, {
    $set: {
    b: 2}});
        assert.equal(2, r.matchedCount);
        assert.equal(2, r.modifiedCount);
        // Upsert a single document
        r = await col.updateOne({
    a: 3}, {
    $set: {
    b: 3}});
        assert.equal(0, r.matchedCount);
        assert.equal(1, r.upsertedCount);
        // Close connection
        client.close();
    } catch(err) {
        console.log(err.stack);
    }
})();
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updateOne和updateMany方法接收第三个参数options，可以用来配置写关注、更新并插入等参数，具体参数列表见：mongodb.github.io/node-mongod…。

3 删除文档

Collection类的deleteOne和deleteMany方法可以用来删除文档。

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
// Connection URL
const url = 'mongodb://localhost:27017';
// Database name
const dbName = 'myproject';
const client = new MongoClient(url);
(async function () {
    try {
        await client.connect();
        console.log("Connected correctly to server");
        const db = client.db(dbName);
        // Get the collection to remove
        const col = db.collection('removes');
        // Insert some documents
        let r = await col.insertMany([{
    a: 1}, {
    a: 2}, {
    a: 2}]);
        assert.equal(3, r.insertedCount);
        // Remove a single document
        r = await col.deleteOne({
    a: 1});
        assert.equal(1, r.deletedCount);
        // Remove multiple documents
        r = await col.deleteMany({
    a: 2});
        assert.equal(2, r.deletedCount);
        // Close connection
        client.close();
    } catch(err) {
        console.log(err.stack);
    }
})();
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deleteOne和deleteMany方法可以接收第二个参数options，用来配置写关注等参数，具体参数列表见：mongodb.github.io/node-mongod…。

4 查询文档

查询MongoDB的主要方法是find方法。find方法返回一个用来操作数据的游标。下面的代码限制查询个数为2条文档，并使用toArray方法导出文档。

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
// Connection URL
const url = 'mongodb://localhost:27017';
// Database name
const dbName = 'myproject';
const client = new MongoClient(url);
(async function () {
    try {
        await client.connect();
        console.log("Connected correctly to server");
        const db = client.db(dbName);
        // Get the collection
        const col = db.collection('find');
        // Insert some documents
        const r = await col.insertMany([{
    a: 1}, {
    a: 1}, {
    a: 1}]);
        assert.equal(3, r.insertedCount);
        // Get first two documents that match the query
        const docs = await col.find({
    a: 1}).limit(2).toArray();
        assert.equal(2, docs.length);
        // Close connection
        client.close();
    } catch(err) {
        console.log(err.stack);
    }
})();
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方法find返回的游标支持各种链式调用，具体支持的方法见：mongodb.github.io/node-mongod…。例如下面的代码使用游标的next方法进行迭代：

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
// Connection URL
const url = 'mongodb://localhost:27017';
// Database name
const dbName = 'myproject';
const client = new MongoClient(url);
(async function () {
    try {
        await client.connect();
        console.log("Connected correctly to server");
        const db = client.db(dbName);
        // Get the collection
        const col = db.collection('find');
        // Insert some documents
        const r = col.insertMany([{
    a: 1}, {
    a: 1}, {
    a: 1}]);
        assert.equal(3, r.insertedCount);
        // Get the cursor
        const cursor = col.find({
    a: 1}).limit(2);
        // Iterate over the cursor
        while(await cursor.hasNext()) {
            const doc = cursor.next();
            console.dir(doc);
        }
        // Close connection
        client.close();
    } catch(err) {
        console.log(err.stack);
    }
})();
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下面的代码使用游标的each方法进行迭代：

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
// Connection URL
const url = 'mongodb://localhost:27017';
// Database Name
const dbName = 'myproject';
const client = new MongoClient(url);
(async function () {
    try {
        await client.connect();
        console.log("Connected correctly to server");
        const db = client.db(dbName);
        const col = db.collection('find');
        const r = await col.insertMany([{
    a:1}, {
    a:1}, {
    a:1}]);
        assert.equal(3, r.insertedCount);
        col.find({
    a: 1}).limit(2).each((err, doc) => {
            if (doc) {
                console.dir(doc);
            } else {
                client.close();
                return false;
            }
        });
    } catch(err) {
        console.log(err.stack);
    }
})();
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5 投影

默认情况下，查询会返回文档的所有字段，可以通过投影(projection)来限制MongoDB服务返回的字段。投影配置文档用来控制返回包含哪些字段、不包含哪些字段：

{ field1: <value>, field2: <value> ... }
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<value>为0或false表示不包含，1或true表示包含。_id字段默认返回，无需配置。除了_id字段外，其他所有字段的配置不可以同时出现0和1。下面的例子仅返回age字段：

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
// Connection URL
const url = 'mongodb://localhost:27017';
// Database Name
const dbName = 'myproject';
const client = new MongoClient(url);
(async function () {
    try {
        await client.connect();
        console.log("Connected correctly to server");
        const db = client.db(dbName);
        const col = db.collection('project');
        let r = await col.insertMany([{
    name: 'Jim', age: 18}, {
    name: 'Lucy', age: 16}]);
        assert.equal(2, r.insertedCount);
        r = await col.find({
    name: 'Jim'}).project({
    age: 1, _id: 0}).toArray();
        console.log(r);
        // Close connection
        client.close();
    } catch (err) {
        console.log(err.stack);
    }
})();
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