Satayjit-Biswas/MongoDB-And-Mongoose

Getting Started

MongoDB :

Get started MongoDB and Following: MongoDB.com

MongoDB Operator :

Get started MongoDB Operator and Following: Operator

Comparison Query Operators:

In this example , "practice" is a Database collection.

$eq Matches values that are equal to a specified value.

  db.practice.find(
      { age: { $eq: 18 } }
    )

$gt Matches values that are greater than a specified value.

  db.practice.find(
      { age: { $gt: 22 } }
    )

$gte Matches values that are greater than or equal to a specified value

  db.practice.find(
      { age: { $gte: 24 } }
    )

$in Matches any of the values specified in an array.

  db.practice.find(
      { age: { $in: [26,17] } }
    )

$lt Matches values that are less than a specified value.

  db.practice.find(
      { age: { $lt: 26 } }
    )

$lte Matches values that are less than or equal to a specified value.

  db.practice.find(
      { age: { $lte: 26 } }
    )

$ne Matches all values that are not equal to a specified value.

  db.practice.find(
      { age: { $ne: 26 } }
    )

$nin Matches none of the values specified in an array.

  db.practice.find(
      { age: { $nin: [26,17] } ,
      { gender: {$gt : 24}}}
    )

Logical Query Operators:

$and Joins query clauses with a logical AND returns all documents that match the conditions of both clauses.

 db.practice.find(
      { $and: [
          {age :{ $lt: 24 }},
          {gender: "Female"}
          ] }
    ).project({
        age: 1,
        gender: 1
    })

$not Inverts the effect of a query expression and returns documents that do not match the query expression.

  db.practice.find(
          { age :{ $not:{ $gt:24} }},
          { gender: "Female" }
    ).project({
        age: 1,
        gender: 1
    })

$nor Joins query clauses with a logical NOR returns all documents that fail to match both clauses.

  db.practice.find(
          {$nor:[
              { age :{ $lte:23} },
              { gender: "Female" }
          ]}
    ).project({
        age: 1,
        gender: 1
    })

$or Joins query clauses with a logical OR returns all documents that match the conditions of either clause.

  db.practice.find(
      { $or: [
          {age :{ $gt: 17 }},
          {gender: "Female"}
          ] }
    ).project({
        age: 1,
        gender: 1
    })

Element Query Operators:

$exists Matches documents that have the specified field.

  db.practice.find(
              { skills :{ $exists : true} },
    ).project({
        skills: 1,
    })

$type Selects documents if a field is of the specified type.

  db.practice.find(
              { skills :{ $type : 'int' } },
    ).project({
        skills: 1,
    })

Aggregation Query Operations:

What is aggregation in mongodb ?

Aggregation is a way of processing a large number of documents in a collection by means of passing them through different stages. The stages make up what is known as a pipeline. The stages in a pipeline can filter, sort, group, reshape and modify documents that pass through the pipeline.

This is an example of the aggregation pipeline syntax:

  pipeline  = [
        { $match : { … } },
        { $group : { … } },
        { $sort : { … } }
       ]

Some Example for aggregation :

$match Stage - Selects documents if a field is of the specified type.

  db.practice.aggregate(
    {
      $match : {
          gender : 'Male' ,
          age : {$gt :18}
      }
    }
  )

If you want to use project then:

  db.practice.aggregate(
    {
      $match : {
          gender : 'Male' ,
          age : {$gt :18}
      }
    },
    {
      $project: {
        gender: 1 ,
        age: 1
      }
    }
  )