MongoDB Exercise - Restaurants with less than 5 grades

Write a MongoDB query to find the restaurants that have at least one grade with a score of less than 5.

Structure of 'restaurants' collection :

{
  "address": {
     "building": "1007",
     "coord": [ -73.856077, 40.848447 ],
     "street": "Morris Park Ave",
     "zipcode": "10462"
  },
  "borough": "Bronx",
  "cuisine": "Bakery",
  "grades": [
     { "date": { "$date": 1393804800000 }, "grade": "A", "score": 2 },
     { "date": { "$date": 1378857600000 }, "grade": "A", "score": 6 },
     { "date": { "$date": 1358985600000 }, "grade": "A", "score": 10 },
     { "date": { "$date": 1322006400000 }, "grade": "A", "score": 9 },
     { "date": { "$date": 1299715200000 }, "grade": "B", "score": 14 }
  ],
  "name": "Morris Park Bake Shop",
  "restaurant_id": "30075445"
}

Query:

db.restaurants.find({ "grades.score": { $lt: 5 } })

Output:

{ "_id" : ObjectId("6422c0161238e3bec47ca5ff"), "address" : { "building" : "1007", "coord" : [ -73.856077, 40.848447 ], "street" : "Morris Park Ave", "zipcode" : "10462" }, "borough" : "Bronx", "cuisine" : "Bakery", "grades" : [ { "date" : { "$date" : 1393804800000 }, "grade" : "A", "score" : 2 }, { "date" : { "$date" : 1378857600000 }, "grade" : "A", "score" : 6 }, { "date" : { "$date" : 1358985600000 }, "grade" : "A", "score" : 10 }, { "date" : { "$date" : 1322006400000 }, "grade" : "A", "score" : 9 }, { "date" : { "$date" : 1299715200000 }, "grade" : "B", "score" : 14 } ], "name" : "Morris Park Bake Shop", "restaurant_id" : "30075445" }
{ "_id" : ObjectId("6422c0161238e3bec47ca601"), "address" : { "building" : "351", "coord" : [ -73.98513559999999, 40.7676919 ], "street" : "West   57 Street", "zipcode" : "10019" }, "borough" : "Manhattan", "cuisine" : "Irish", "grades" : [ { "date" : { "$date" : 1409961600000 }, "grade" : "A", "score" : 2 }, { "date" : { "$date" : 1374451200000 }, "grade" : "A", "score" : 11 }, { "date" : { "$date" : 1343692800000 }, "grade" : "A", "score" : 12 }, { "date" : { "$date" : 1325116800000 }, "grade" : "A", "score" : 12 } ], "name" : "Dj Reynolds Pub And Restaurant", "restaurant_id" : "30191841" }
.....

Explanation:

The said query in MongoDB that returns all documents in the 'restaurants' collection that have at least one grade with a score of less than 5.

The specified condition searches for documents where the "grades" field contains at least one sub-document where the "score" field has a value less than 5.

Note: This output is generated using MongoDB server version 3.6

Improve this sample solution and post your code through Disqus.

Previous: Find the restaurant name, borough, longitude and latitude and cuisine for those restaurants which contain Mad as first three letters of its name.
Next: Find the restaurants in Manhattan that have at least one grade under 5.