prathmesh-ka-github / Learning-mongodb

Learning MongoDB. MongoDB is a source-available, cross-platform, document-oriented database program.

Learning MongoDB.

MongoDB is a source-available, cross-platform, document-oriented database program. Classified as a NoSQL database product, MongoDB utilizes JSON-like documents with optional schemas. MongoDB is developed by MongoDB Inc. and current versions are licensed under the Server Side Public License.

Basic commands for MongoDB Shell.

1. To show Databases -

> show dbs

2. To use/connect to a Database OR to make new Databse -

> use database-name

3. To make new collection -

> db.createCollection("collection-name")

4. To drop a Database (you need to be in that database) -

> use school
> db.dropDatabase()
    //deletes current database

5. Inserting document in a database. In MongoDB we save data by inserting documents in the collection. Same as key:value pairs in JSON -

> use school
    //using database school.

> db.createCollection("students")
    //creating new collection named students.

> db.students.insertOne({name:'Spongebob', age:30, gpa:3.2})
    //inserting one document into the collection.

6. To show contents of a collection.

> db.students.find()

//multiple fiters
> db.students.find({gpa:4.0, fullTime:true})

7. Projection.

//syntax
> db.students.find({-filter-}, {-projection-})


//examples
> db.students.find({fullTime:true}, {name:true, _id:false})

> db.students.find({}, {name:true, gpa:true, _id:false})

8. Sorting and limiting.

//syntax
> db.-collectionName-.find().sort({-field- : -ascending(1) and decending(-1)-})

> db.-collectionName-.find().limit(-limitNumber-)



//examples
> db.students.find().sort({name:1})
    //this will sort the outputs by name and ascending order

> db.students.find().limit(2)
    //this will limit results to 2

//both sorting and limiting
> db.students.find().sort({gpa:1}).limit(5)

9. Update fields.

//update one
//syntax
> db.students.updateOne({-selection criteria-}, {$set:{-update field:value-}})


//examples
>db.students.updateOne({name:'Spongebob'}, {$set:{fullTime:true}})


//update many
//syntax
> db.students.updateMany({-selection criteria-}, {$set:{-update field:value-}})

//examples
//$exists checks if does the document has that field.
> db.students.updateMany({fullTime:{$exits:false}}, {$set:{fullTime:true}})