CRUD Operations in MongoDB

Insert Operation

Documents can be inserted using insertOne() and insertMany() methods.

db.<collectionname>.insertOne({field1:value1, field2: value2})

db.<collectionname>.insertMany([
{field1:value1, field2: value2},
{field1:value1,field2:value2}
])

Let us see an Example:

Insert one document in a collection named fruits

 db.fruits.insertOne({ Name:"Mango", season: "Summer", isAvailable:true})

Insert multiple documents in a collection named fruits

 db.fruits.insertMany([
 { Name:"Water Melon", season: "Summer", isAvailable:true},
 { Name:"Custard Apple", season: "Monsoon", isAvailable:true},
 { Name:"Pomo granate", season: "Monsoon", isAvailable:true}
 ])

Read Operation

Documents in collections can be retrieved by using find() method.

db.<collectionname>.find(<query>,<projection>)

Let us see with an example:

Finding all the documents or fruits which are available in summer
```
 db.fruits.find({season:"Summer"})
```
To get certain number of top documents or fruits whose value of season is "Summer" limit() method is used.
```
 db.fruits.find({season:"Summer"}).limit(3)
```
To skip certain number of top documents skip() method is used.
```
 db.fruits.find({season:"Summer"}).skip(1)
```

Update Operation

To update a document in a collection in MongoDB, you can use the update() or updateOne() method. Here's an example of how to update a document using the MongoDB shell. The following are the syntax to update single and multiple documents

updateOne()

db.colname.updateOne(
  { _id: ObjectId("yourDocumentId") }, // The query to match the document
  { $set: { keyToUpdate: newValue } }  // The update operation using $set
);

updateMany()

db.colname.updateMany(
{keytomatch :valuetomatch},// The query to match the document
{$set:{keytoupdate: newvalue}} // The update operation using $set
);

Let us see with an example:

To update an only one document from isAvailable: true to isAvaiable: false .

 dob.fruits.updateOne({isAvailable:true},
 {$set:
 {isAvailable:false}}
 );

To update all documents in collection from key-value as isAvailable: true to isAvailable: false.
```
 dob.fruits.updateMany({isAvailable:true},
 {$set:{isAvailable:false}}
 );
```

Delete Operation

To delete documents from a collection in MongoDB, you can use the deleteOne() or deleteMany() method, depending on whether you want to delete a single document or multiple documents that match certain criteria.

The syntax for the delete query:

deleteOne()

db.collname.deleteOne({keytofind:valuetofind})

deleteMany()

db.collname.deleteMany({keytofind:valuetofind})

Let us understand with an example:

The query to delete the first and only one document that contains key-value pair season: "Summer"
```
 db.fruits.deleteOne({season: "Summer"})
```
The query to delete all the documents that contain key-value pair season: "Summer"
```
 db.fruits.deleteMany({season: "Summer"})
```

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