In this article we are going to learn a few basic queries for Creating, Updating and Deleting the database components.
Learning Queries to play around with the database:
We will classify the queries into 2 groups:
- Queries to handle the database hierarchy.
- Queries to search and retrieve records using some search parameter.
Queries to handle the database hierarchy:
Creating a new database To create a new database, you can use the command
use db_name
The same command is also used to switch between the available db’s. To list the available db’s:
show dbs
NOTE: A newly created database won’t be listed unless you insert a new record into the DB.
Drop database To drop a database, use the command,
db.dropDatabase()
This will drop the current database along with all the collections and records present in the database. So before dropping another database a user needs to switch to that particular database before deleting the same.
Creating a Collection Switch to the DB where you want to create a new Collection, then you can run the below command
db.createCollection("your_collection_name")
Listing available collections To list all the available collections inside a database:
show collections
Listing all the records present in a collection To see all records available in a single collection you can use the below command,
db.collection_name.find()
Rename collection To change the name of an existing collection,
db['curent_name_of_the_collection'].renameCollection('new_name_of_the_collection')
Drop collection To drop a collection along with all the records inside it:
db.collection_name.drop()
Inserting a new document ( JSON object) into the collection If I want to insert a JSON object with details as given in the example below into a collection named Test the query would be like this,
db.collection_name.insert({JSON_object})
Ex: db.Test.insert({"First name" : Mithlesh, "Last name" : "Thiyari"})
Remove document To remove a particular document from some collection, we need to give the Identity of the document enclosed within the parenthesis.
db.collection_name.remove({'Identity of document which needs to be removed'})
Ex: db.Test.remove({"First name":"Mithlesh", "Last name": "Thiyari"})
Remove all documents This command deletes all the documents present inside a Collection making the collection empty.
db.collection_name.remove()