MongoDB Exercise - Find the lowest score for each cuisine
Write a MongoDB query to find the lowest score for each cuisine.
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([
{
$unwind: "$grades"
},
{
$group: {
_id: "$cuisine",
minScore: { $min: "$grades.score" }
}
}
])
Output:
{ _id: 'Middle Eastern', minScore: 2 }, { _id: 'Jewish/Kosher', minScore: 0 }, { _id: 'Hotdogs', minScore: 0 }, { _id: 'Polish', minScore: 2 }, { _id: 'Asian', minScore: 2 }, { _id: 'Soul Food', minScore: 2 }, { _id: 'Eastern European', minScore: 2 }, { _id: 'Vegetarian', minScore: 5 }, { _id: 'Czech', minScore: 8 }, { _id: 'Spanish', minScore: 2 }, { _id: 'Juice, Smoothies, Fruit Salads', minScore: 0 }, { _id: 'Pancakes/Waffles', minScore: 3 }, { _id: 'Latin (Cuban, Dominican, Puerto Rican, South & Central American)', minScore: 0 }, { _id: 'Barbecue', minScore: 5 }, { _id: 'Ice Cream, Gelato, Yogurt, Ices', minScore: 0 }, { _id: 'Japanese', minScore: 0 }, { _id: 'Indian', minScore: 0 }, { _id: 'Bangladeshi', minScore: 7 }, { _id: 'Donuts', minScore: 0 }, { _id: 'Salads', minScore: 2 } .....
Explanation:
The given query in MongoDB provides a simple and efficient way to find the _id, which is the cuisine name, and minScore as minimum score for each cuisine in the restaurants collection.
The $unwind stage is used to break down the grades array into individual documents.
The $group grouped the documents by cuisine and use the $min operator to calculate the minimum score for each group.
Note: This output is generated using MongoDB server version 3.6
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https://www.w3resource.com/mongodb-exercises/mongodb-exercise-63.php
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