在Node.js MongoDB中通过ID查找文档

Question

我想通过 ID 查找特定文档，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"
}
]

我有一个学生列表，想用GET方法查找特定的ID。例如，假设我想找到这个：

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

这是我查找 ID 的代码，请让我知道需要修复的地方。

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);
     }

   });
});

之前我使用的是findOne方法，但那只能找到第一个文档的出现，这不是我想要的。

- Arnald

---

@franiis 所以在我的代码中，如果我想要查找 { "_id": "5d0381ad681a2a3aa1dc5874", "role_num": 3, "first_name": "Adi", "last_name": "Ad", "marks": 89 } 的文档， - Arnald

@franiis，我在代码中可以更改什么，而且我不想硬编码这些值。 - Arnald

我不是Node.js开发人员。在数据库通信中，通过“id”查询数据库是最重要的任务。也许可以参考这个链接：https://dev59.com/fmcs5IYBdhLWcg3wiEiK（我相信一定有一些示例）。 - franiis

Answer 1

缺少new

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

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

- Puser

---

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

Answer 2

被接受的答案不是有效的语法，正确的语法应该是：

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

- Asad Madni

Answer 3

从Mongo中获取带有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，因为不能有两个具有相同ID的记录。

- NadavM

---

我应该在哪里定义像"_id": id这样的 ID？ - Arnald

我的代码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}); // 处理响应 - NadavM

同样的操作也可以不使用异步实现： db.collection('students').findOne({"id": id}, function(err, result) {//处理结果和错误}) - NadavM