All possible question's answer by aggregation framework of mongoDB for Movies DATASET. movies data | data science | aggregation | mongoDB

MongoDB: Aggregation Framework.js

#### Format of Dataset
    # Movies
    {
        "_id" : ObjectId("5aa7d4496b7a5451ba8ce741"),
        "movie_id" : 1,
        "title" : "Toy Story (1995)",
        "genres" : "Animation|Children's|Comedy"
    }
    # Ratings
    {
        "_id" : ObjectId("5aa7d3f96b7a5451ba8b6ef5"),
        "user_id" : 1,
        "movie_id" : 3408,
        "rating" : 4,
        "ts" : 978300275
    }
    # Users
    {
        "_id" : ObjectId("5aa7d4656b7a5451ba8d7858"),
        "user_id" : 1,
        "gender" : "F",
        "age" : 1,
        "occupation" : 10,
        "zip" : 48067
    }

# Total movies released in this(YEAR) year:-
db.getCollection('movies').aggregate([
    {$match:{"title":{$regex:"YEAR"}}},
    {$project:{ "title":1,"length":{$strLenCP: "$title"} }},
    {$project:{"title":1,"yearOfRelease":{$substr:["$title",{$subtract:["$length",5]},4]}}},
    {$group:{_id:"$yearOfRelease",total:{"$sum":1}}}
])

# No of Movies released in year group by YEAR :-
db.getCollection('movies').aggregate([
    {$project:{ "title":1,"length":{$strLenCP: "$title"} }},
    {$project:{"title":1,"yearOfRelease":{$substr:["$title",{$subtract:["$length",5]},4]}}},
    {$group:{_id:"$yearOfRelease",total:{"$sum":1}}}
])

# Movie status based on rating(Good or Bad)
db.getCollection('ratings').aggregate([
{
    $project:{
        summary:{
            $cond:[{$gte:["$rating",2.5]},"Good Movie","Bad Movie"]
           }
    `}
 }
],{allowDiskUse:true});

# Movie status based on rating(Good or Bad or Average)
db.getCollection('ratings').aggregate([
{
$project:{
    summary:{
        $switch:{
                branches:[
                    {
                        case:{$gt:["$rating",2.5]},
                        then: "Good Movie"
                    },
                    {
                        case:{$eq:["$rating",2.5]},
                        then: "Average Movie"
                     },
                     {
                        case:{$lt:["$rating",2.5]},
                        then: "Bad Movie" 
                      }
                ]
            }
   }}}
],{allowDiskUse:true});

##Number of Movies group by Geners
  # Number of Movies group by Geners($group+$sort)
    db.getCollection('movies').aggregate([
        {
            $project:{ 
                "title":1,
                "genres":{$split: ["$genres",'|']} 
            }
        },
        {
            $unwind:"$genres"
        },
        {
            $group:{
                _id:"$genres",
                total:{ $sum:1 }
            }
        }
    ])
  # Number of Movies group by Geners($sortByCount)
    db.getCollection('movies').aggregate([
        {
            $project:{ 
                "title":1,
                "genres":{$split: ["$genres",'|']} 
            }
        },
        {
            $unwind:"$genres"
        },
       { $sortByCount: "$genres" }
    ])
    
# Lowest, Highest and Average Rating of a Movie(MOVIEID)
db.getCollection('movies').aggregate([
    {
        $match:{"movie_id":MOVIEID}
    },
    {
        $lookup:{
            from:"ratings",
            localField:"movie_id",
            foreignField:"movie_id",
            as:"movie_ratings"
        }
    },
    {
        $unwind:"$movie_ratings"},
    {
        $sort:{"movie_ratings.rating":1}},
    {
        $group:{
            _id:"$title",
            "lowestRating":{"$first":"$movie_ratings.rating"},
            "highestRating":{"$last":"$movie_ratings.rating"},
            "averageRating":{"$avg":"$movie_ratings.rating"}
        }
    }
])

# List Movies with Highest Reviews on Top
db.getCollection('movies').aggregate([
    {
        $lookup:{
            from:"ratings",
            localField:"movie_id",
            foreignField:"movie_id",
            as:"ratings"
           }
    },
    {
        $project:{
           "movie_id":"$movie_id",
           "movieName":"$title",
           "noOfReviews":{$size:"$ratings"}
           }
    },
    {   
        $sort:{"noOfReviews":-1}
    }
],
{allowDiskUse:true})