Introduction
Assuming that the database is already created in the mongoDB shell. We can perform CRUD operations like create, read, update, and delete documents. A document is basically a record in MongoDB. It is a data structure composed of field and value pairs. MongoDB documents are similar to JSON objects. The values of fields may include other documents, arrays, and arrays of documents.
Prerequisites
- Install mongodb-community
- Refer to the blog Create database in MongoDB for installing using brew and connect to the MongoDB Shell
Create database command
Execute the following command to create a database with name sample_db
> use sample_db
CRUD Operations
Insert a single Document
To insert a single document in the collection, execute db.collection.insertOne()
Note: If the -id field is not specifies then MongoDb adds the id field with ObjectId value to the document inserted.
db.users.insertOne({first-name: "Anchal", last-name:"Gupta", age: 24})
Insert Multiple Documents
We can insert multiple documents in the collection by using db.collection.insertMany() command.
db.departments.insertMany([
{
name: "sales",
people: 10,
},
{
name: "backend",
people: 15,
},
]);
Read All Documents in a Collection
To read all the documents (data) in a collection, execute db.collection.find()
It will return all the documents inside a collection.
Read documents by specifying field and value
To read any specific document, we can specify the field and value with the command db.document.find({"field": "value"})
It will return the documents that match the specifications.
We can also specify query filters and add more specifications
Example: The following query will return upto 5 users of age greater than 18.
db.users.find(
{age: {$gt: 18} }
).limit(5)Update single document
Update commands are used to modify the existing documents in a collection.
To update a document in the collection, execute db.collection.updateOne() along with the update operators such as $set to modify field values.
db.departments.updateOne(
{
name:"sales",
},
{
$set: {
people:20,
}
})The first document where name equals sales will be updated.
Update multiple document
To update multiple document, execute the command db.departments.updateMany() .
db.departments.updateMany(
{people: {$gt:10},
{
$set:{location:"tokyo"},
})It will update all the documents where people are greater than 10
Replace a document
To replace entire content of the document expect the _id field, pass the new document as the second argument and execute the command db.departments.replaceOne() .
While executing the replace command, do not include the update operators expression.
db.departments.replaceOne(
{name:"sales"},
{name:"design", people:8}
)It will replace the document where name is equal to the sales with the new document {name:"design", people:8} passed as the second arguement
Delete one document
To delete a document from the collection, execute the command db.collection.deleteOne() .
db.departments.deleteOne({name:"design"})It will delete the first document where the name is equal to design
Delete documents that match the condition
To delete multiple documents from the collection, execute the command db.collection.deleteMany() .
db.departments.deleteMany({location:"tokyo"})It will delete all the documents from the collection where location is equal to tokyo
Delete all documents
To delete all the documents from the collection, execute the command db.departments.deleteMany({})
Conclusion
I tried executing the MongoDB crud operations (create, read, update, delete) using the MongoDB shell. CRUD operations describe the conventions of a user-interface that let users view, search, and modify parts of the database.
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