Display results according to calendar weeks in Mongodb - mongodb

Question

I have a MongoDB collection named Bookings
{
"_id" : ObjectId("5fca982d219fee6f00e631a0"),
"price" : 45.9,
"createdAt" : ISODate("2020-12-04T20:12:29.117Z")
}
{
"_id" : ObjectId("5fca990b219fee6f00e631a1"),
"price" : 45.9,
"createdAt" : ISODate("2020-12-04T20:16:11.925Z")
}
{
"_id" : ObjectId("5fcab925a912a2064fe7b916"),
"price" : 45.9,
"createdAt" : ISODate("2020-12-04T22:33:09.958Z")
}
{
"_id" : ObjectId("5fcab938a912a2064fe7b917"),
"price" : 45.9,
"createdAt" : ISODate("2020-12-04T22:33:28.641Z")
}
{
"_id" : ObjectId("5fcab94aa912a2064fe7b918"),
"createdAt" : ISODate("2020-12-04T22:33:46.118Z")
}
{
"_id" : ObjectId("5fcb73e0e396cf18e6141dc6"),
"price" : 45.9,
"createdAt" : ISODate("2020-12-05T11:49:52.544Z")
}
{
"_id" : ObjectId("5fcb73eee396cf18e6141dc7"),
"price" : 45.9,
"createdAt" : ISODate("2020-12-05T11:50:06.914Z")
}
{
"_id" : ObjectId("5fcbee785ef206248fa9513e"),
"price" : 35.7,
"createdAt" : ISODate("2020-12-05T20:32:56.508Z")
}
{
"_id" : ObjectId("5fcbf0045ef206248fa9513f"),
"price" : 2047.66,
"createdAt" : ISODate("2020-12-05T20:39:32.369Z")
}
I need to display the data according to a week and collective price for that week. If I use aggregation pipeline, It would only give me the range of dates on which booking is made.
{$group: {
_id: {
$week: "$createdAt"
},
start_date: {$min: "$createdAt"},
end_date: {$max: "$createdAt"}
}}
Suppose the previous week started from 14-06-21 and ended on 20-06-21
Instead, I want a result which would actually include start_date as 14-06-21 and end_date as 20-06-21, and if no earning is made it would be 0 otherwise the total price in a given week and so on for other group of weeks for whole year or month accordingly.

Answer 1

You can categorize total price by week number using $week operator, but it is hard to get the week's start date and end date in MongoDB, I would suggest you to get start date and end date from the week number in your client-side language.
$group by createdAt's week using $week operator and get total price by $sum
db.collection.aggregate([
{
$group: {
_id: { $week: "$createdAt" },
totalPrice: { $sum: "$price" }
}
}
])
Playground

Answer 2

For fetching the start day of a week, you can make use of the $dateToString operator and pass the %g and %v in format which represents ISO Year and Week of the year respectively.
Similarly, add 518400000 (6 days in milliseconds) to the start date of the week to get the end date.
Also, these two operations will only work inside the _id field of the $group stage, so parse the sub-object of the _id key to get the required data values. The weekNo key is useless for the $group stage, but keep it if it's required.
db.collection.aggregate([
{
$group: {
_id: {
"weekNo": {
$week: "$createdAt"
},
"start_date": {
"$dateFromString": {
"dateString": {
"$dateToString": {
"date": "$createdAt",
"format": "%G/%V",
},
},
"format": "%G/%V"
}
},
"end_date": {
"$add": [
{
"$dateFromString": {
"dateString": {
"$dateToString": {
"date": "$createdAt",
"format": "%G/%V",
},
},
"format": "%G/%V"
}
},
518400000,
],
},
},
totalPrice: {
$sum: "$price"
}
}
}
])
Mongo Playground Sample Execution