The content of this page has been automatically translated by AI. If you encounter any problems while reading, you can view the corresponding content in Chinese.
Help & Documentation>TencentDB for MongoDB>Quick Start>Reading/Writing Database

Reading/Writing Database

Last updated: 2025-02-08 10:10:02

On this page:

After connecting to the database, you can create a database and write data.

Creating a Database

The syntax format for creating a database in MongoDB is as follows: 
use DATABASE_NAME
Create a database named myfirstdb and insert a document.
> use myFirstDB
switched to db myFirstDB
> db.myFirstDB.insert({"test":"myFirstDB"})
WriteResult({ "nInserted" : 1 })
Query the created database.
> show dbs
admin      0.000GB
config     0.000GB
local      0.041GB
myFirstDB  0.000GB

Creating a collection

In MongoDB, the createCollection() method is used to create a collection. Syntax format:
db.createCollection(name, options)
Parameter description:
name: Name of the collection to be created.
options: Optional parameters specifying options related to memory size and indexes.
Options Field
Type
Description
capped
BOOL
Indicates whether to set the maximum byte size of the collection. If true, the size parameter must be set. Default is false.
autoIndexId
BOOL
Set whether to automatically create an index. If true, an index is automatically created on the _id field. Default is false.
size
Value
Set the maximum number of bytes for the collection.
max
Value
Set the maximum number of documents in the collection.
Example of creating the firstcol collection in the myfirstdb database:
> use myFirstDB
switched to db myFirstDB
> db.createCollection("FirstCol")
{
        "ok" : 1,
        "$clusterTime" : {
                "clusterTime" : Timestamp(1634821900, 2),
                "signature" : {
                        "hash" : BinData(0,"WFu7yj8wjeUBWG3b+oT84Q8wIw8="),
                        "keyId" : NumberLong("6990600483068968961")
                }
        },
        "operationTime" : Timestamp(1634821900, 2)
}
View the created collection:
> show collections
FirstCol
Create the firstcol collection with a maximum size of 6142800B and a maximum of 10000 documents, example as follows:
> db.createCollection("FirstCol", { capped : true, autoIndexId : true, size : 6142800, max : 10000 } )
{
        "note" : "the autoIndexId option is deprecated and will be removed in a future release",
        "ok" : 1,
        "$clusterTime" : {
                "clusterTime" : Timestamp(1634821879, 1),
                "signature" : {
                        "hash" : BinData(0,"EuIbp2fu9Yh38HOBHLgYqljdKaE="),
                        "keyId" : NumberLong("6990600483068968961")
                }
        },
        "operationTime" : Timestamp(1634821879, 1)
}

Inserting Documents

MongoDB uses the insert() or save() method to insert documents into the collection, example as follows:
> db.FirstCol.insert({name:"Li Si",sex:"Female",age:25,status:"A"})
WriteResult({ "nInserted" : 1 })
Viewing Inserted Documents in the Collection:
> db.FirstCol.find()
{ "_id" : ObjectId("61716957a6fe1ef4d7eae979"), "name" : "Li Si", "sex" : "Female", "age" : 25, "status" : "A" }
db.collection.insertMany() is used to insert one or more documents into the collection. The syntax format is as follows:
db.collection.insertMany(
 [ <document 1> , <document 2>, ... ]
 )
For example:
> db.FirstCol.insertMany([{name:"Li San",sex:"Female",age:25,status:"A"},{name:"Wang Liu",sex:"Male",age:26,status:"B"},{name:"Harry Smith",sex:"Male",age:26,status:"A",groups:["news","sports"]}])
{

      "acknowledged" : true,
      "insertedIds" : [
              ObjectId("617282a3a4bb72d733b5c6d7"),
              ObjectId("617282a3a4bb72d733b5c6d8"),
              ObjectId("617282a3a4bb72d733b5c6d9")
      ]
}

Updating the Database

MongoDB uses update() to update documents in the collection.
Example of updating data in the FirstCol collection where name is Li San:
> db.FirstCol.update({name:"Li San", sex:"Female", age:25, status:"A"}, {$set:{'age':28}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
Query modification results:
> db.FirstCol.find().pretty()
{
        "_id" : ObjectId("618904b6258a6c38daf13abd"),
        "name" : "Li San",
        "sex" : "Female",
        "age" : 28,
        "status" : "A"
}
{
        "_id" : ObjectId("618904b6258a6c38daf13abe"),
        "name" : "Wang Liu",
        "sex" : "Male",
        "age" : 26,
        "status" : "B"
}
{
        "_id" : ObjectId("618904b6258a6c38daf13abf"),
        "name" : "Wang Wu",
        "sex" : "Male",
        "age" : 26,
        "status" : "A",
        "groups" : [
                "news",
                "sports"
        ]
}

Delete Database

MongoDB uses remove() to delete documents in the collection. Example:
> db.FirstCol.remove({name:"Li San",sex:"Female",age:28,status:"A"})
WriteResult({ "nRemoved" : 1 })
Query delete results:
> db.FirstCol.find().pretty()
{
        "_id" : ObjectId("618904b6258a6c38daf13abe"),
        "name" : "Wang Liu",
        "sex" : "Male",
        "age" : 26,
        "status" : "B"
}
{
        "_id" : ObjectId("618904b6258a6c38daf13abf"),
        "name" : "Wang Wu",
        "sex" : "Male",
        "age" : 26,
        "status" : "A",
        "groups" : [
                "news",
                "sports"
        ]
}

More information

For more operation methods, please see MongoDB official documentation.
中国站 - English