How to create database in MongoDB

MongoDB doesn’t provides any command to create “database” , and you don’t need to create it manually as well. Because, MangoDB will create it on the fly, during the first time you save the value into the defined collection, and database.

For developer from SQL backgroud, we need to create a database, then table and insert the values into the newly created table. In MongoDB, you don’t need to mention what you want to create, when first time you save the value into the defined collection, under selected database, MangoDB will create the value, collection and database automatically.

In this guide, we show you how and when MongoDB creates the database and collections.

1. Show all database

Use “show dbs” to display all the available databases.

MongoDB shell version: 1.8.1
connecting to: test
> show dbs
admin   0.03125GB
local   (empty)

Only two databases : “admin” and “local” available.

2. Define a database name

Issue “use new-databasename” to switch to the define database (even non-exists database name will work). However, MangoDB will not create any database yet, until you save something inside.

> use mkyongdb
switched to db mkyongdb
> show dbs
admin   0.03125GB
local   (empty)

Database “mkyongdb” is not create yet.

3. Save It

Define a collection named “users“, and save a dummy document(value) inside.

> db.users.save( {username:"mkyong"} )
> db.users.find()
{ "_id" : ObjectId("4dbac7bfea37068bd0987573"), "username" : "mkyong" }
>
> show dbs
admin   0.03125GB
local   (empty)
mkyongdb        0.03125GB

This says, “save the document ‘{username:”mkyong”}’ into the ‘user’ collection”. When this “save” operation is performed, MangoDB will create the “user” collection, and “mkyongdb” database automatically.

Note : You can find more similar articles at - Java MongoDB Tutorials

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