MongoDB Exercise - Find the number of 'A'-rated restaurants by cuisine and borough
Write a MongoDB query to find the count of restaurants that received a grade of 'A' for each cuisine and borough.
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.aggregate([
{
$match: { "grades.grade": "A" }
},
{
$group: {
_id: { cuisine: "$cuisine", borough: "$borough" },
count: { $sum: 1 }
}
},
{
$sort: { count: -1 }
}
]);
Output:
{ _id: { cuisine: 'American ', borough: 'Manhattan' }, count: 731 }, { _id: { cuisine: 'Italian', borough: 'Manhattan' }, count: 204 }, { _id: { cuisine: 'American ', borough: 'Queens' }, count: 192 }, { _id: { cuisine: 'American ', borough: 'Brooklyn' }, count: 190 }, { _id: { cuisine: 'Café/Coffee/Tea', borough: 'Manhattan' }, count: 133 }, { _id: { cuisine: 'Pizza', borough: 'Queens' }, count: 80 }, { _id: { cuisine: 'American ', borough: 'Bronx' }, count: 74 }, { _id: { cuisine: 'Pizza', borough: 'Manhattan' }, count: 73 }, { _id: { cuisine: 'Pizza', borough: 'Brooklyn' }, count: 72 }, { _id: { cuisine: 'French', borough: 'Manhattan' }, count: 68 }, { _id: { cuisine: 'Japanese', borough: 'Manhattan' }, count: 68 }, .....
Explanation:
The said query in MongoDB that returns a result set that includes each cuisine-borough pair and the count of restaurants that received a grade of 'A' for that pair.
The $match stage filters the restaurants that received a grade of 'A'. The dot notation have used to access the nested grades array.
The $group stage groups the restaurants by cuisine and borough, and calculates the count of restaurants using the $sum operator.
$sort stage sorts the result by the count in descending order, so that the cuisine-borough pairs with the highest counts appear first.
Note: This output is generated using MongoDB server version 3.6
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https://www.w3resource.com/mongodb-exercises/mongodb-exercise-59.php
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