在nodejs mongodb中通过id查找文档答案

【问题标题】：Find a document by id in nodejs mongodb在nodejs mongodb中通过id查找文档
【发布时间】：2019-11-08 05:46:14
【问题描述】：

所以我想通过 id 找到一个特定的文档，例如

[
{
"_id": "5d0381ad681a2a3aa1dc5872",
"role_num": 1,
"first_name": "Adilf",
"last_name": "Adli",
"marks": 97
},
{
"_id": "5d0381ad681a2a3aa1dc5873",
"role_num": 2,
"first_name": "Mario",
"last_name": "Adl",
"marks": 93
},
{
"_id": "5d0381ad681a2a3aa1dc5874",
"role_num": 3,
"first_name": "Adi",
"last_name": "Ad",
"marks": 89
},
{
"_id": "5d0381ad681a2a3aa1dc5875",
"role_num": 4,
"first_name": "Harold",
"last_name": "Nome",
"marks": 78
},
{
"_id": "5d10b6124adac42c4467cb88",
"role_num": 6,
"first_name": "Mohammed",
"last_name": "Khan",
"marks": 91
},
{
"_id": "5d10b65f4adac42c4467cb89",
"role_num": 6,
"first_name": "Mohammed",
"last_name": "Khan",
"marks": 91
},
{
"_id": "5d10ebc562562921883741a1",
"role_num": 6,
"first_name": "Mohammed",
"last_name": "Khan",
"marks": 91
},
{
"_id": "5d11af3a62562921883741a3",
"role_num": 6,
"first_name": "Mohammed",
"last_name": "Khan",
"marks": 91
},
{
"_id": "5d11b40b62562921883741a4",
"role_num": 6,
"first_name": "Mohammed",
"last_name": "Khan",
"marks": 91
},
{
"_id": "5d11b4cd6dc8db0fe0f489fc",
"role_num": 7,
"first_name": "Masrur",
"last_name": "Ahmed",
"marks": 81
},
{
"_id": "5d11b5131beb7f338414bc96",
"role_num": 7,
"first_name": "Masrur",
"last_name": "Ahmed",
"marks": 81
},
{
"_id": "5d11b56cd0baff00cc616ebb",
"role_num": 7,
"first_name": "Masrur",
"last_name": "Ahmed",
"marks": 81
},
{
"_id": "5d11b586d76c463d30d02355",
"role_num": 7,
"first_name": "Masrur",
"last_name": "Ahmed",
"marks": 81
},
{
"_id": "5d11b74effe56935d88d910e",
"role_num": 7,
"first_name": "Masrur",
"last_name": "Ahmed",
"marks": 81
},
{
"_id": "5d11b7d1e425ab1dbceda262",
"role_num": 7,
"first_name": "Masrur",
"last_name": "Ahmed",
"marks": 81
},
{
"_id": "5d11b90e44b2c61650377951",
"role_num": 7,
"first_name": "Masrur",
"last_name": "Ahmed",
"marks": 81
},
{
"_id": "5d120883a2f4d83bac8441c7",
"first_name": "Maria"
},
{
"_id": "5d1208cca2f4d83bac8441c8",
"first_name": "Maria"
},
{
"_id": "5d12093fa2f4d83bac8441c9",
"first_name": "Maria"
},
{
"_id": "5d1209c0a2f4d83bac8441ca",
"first_name": "Baki"
},
{
"_id": "5d120f0ed9e07909a413cd85",
"role_num": "5",
"first_name": "Arojfsdof",
"last_name": "adfjaf",
"marks": "12"
},
{
"_id": "5d12fff7d9e07909a413cd8a",
"role_num": "17",
"first_name": "BARKS",
"last_name": "DUDUE",
"marks": "45"
},
{
"_id": "5d131c42313e183ae09966c3",
"role_num": "4",
"first_name": "Maam",
"last_name": "Alsad",
"marks": "80"
}
]

上面我有一个学生列表，我想做一个 get 方法来通过 id 找到一个特定的，例如假设我想找到这个

{
    "_id": "5d131c42313e183ae09966c3",
    "role_num": "4",
    "first_name": "Maam",
    "last_name": "Alsad",
    "marks": "80"
}

这是我的查找 ID 代码，让我知道我必须修复什么

second.get('/students/:id', (req, res) => {
   db.collection('students').find({"_id": ObjectID(req.body._id)}).toArray((err,result) => {
     if(!err) {
        res.send(result);
     } else {
         console.log(err);
     }

   });
});

在我使用 findOne 方法之前，该方法仅用于查找第一个文档的出现，这不是我想要的

【问题讨论】：

@franiis 所以如果我想在我的代码中找到 { "_id": "5d0381ad681a2a3aa1dc5874", "role_num": 3, "first_name": "Adi", "last_name": "广告”，“标记”：89 }，
@franiis 我可以在我的代码中更改什么，我不想硬编码这些值
我不是 Node.js 开发人员。通过id查询数据库是数据库通信中最重要的任务。也许是这样：stackoverflow.com/questions/12769252/…（我敢肯定在某处有一些例子）。

标签： node.js mongodb

【解决方案1】：

要从 Mongo 获取带有 ID 的记录，db.collection('students').findOne({"_id:": id}) 是正确的格式。您只能获取一条记录，因为您不能拥有 2 条具有相同 ID 的记录。

【讨论】：

我在哪里定义像“_id”这样的id：id
我的是异步函数的一部分：let client = await MongoClient.connect(uri, {useNewUrlParser: true}); let db = client.db('students'); try { const res = await db.collection('students').findOne({"_id": id}); // do something with response
不用异步也可以做到这一点：db.collection('students').findOne({"id": id}, function(err, result) {//handle result and error})

【解决方案2】：

缺少new

var ObjectID = require('mongodb').ObjectID;   

db.collection('students').find({"_id": new ObjectID(req.body._id)})

【讨论】：

这对我帮助很大。谢谢你。我还需要添加const ObjectID = require('mongodb').ObjectID;