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A single MongoDB query to orderby date and group by user
For this, simply use aggregate() in MongoDB. Let us create a collection with documents −
> db.demo243.insertOne({"userId":1,dueDate:new ISODate("2019-01-10")});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e4575f81627c0c63e7dba5f")
}
> db.demo243.insertOne({"userId":2,dueDate:new ISODate("2019-11-10")});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e4576011627c0c63e7dba60")
}
> db.demo243.insertOne({"userId":2,dueDate:new ISODate("2020-01-31")});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e4576151627c0c63e7dba61")
}
> db.demo243.insertOne({"userId":1,dueDate:new ISODate("2010-01-10")});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e45761b1627c0c63e7dba62")
}Display all documents from a collection with the help of find() method −
> db.demo243.find();
This will produce the following output −
{ "_id" : ObjectId("5e4575f81627c0c63e7dba5f"), "userId" : 1, "dueDate" : ISODate("2019-01-10T00:00:00Z") }
{ "_id" : ObjectId("5e4576011627c0c63e7dba60"), "userId" : 2, "dueDate" : ISODate("2019-11-10T00:00:00Z") }
{ "_id" : ObjectId("5e4576151627c0c63e7dba61"), "userId" : 2, "dueDate" : ISODate("2020-01-31T00:00:00Z") }
{ "_id" : ObjectId("5e45761b1627c0c63e7dba62"), "userId" : 1, "dueDate" : ISODate("2010-01-10T00:00:00Z") }Following is the query to orderby date and group by user −
> db.demo243.aggregate({
... $group: {
... _id : '$userId',
... dueDate: { $max: '$dueDate'}
... }
...})This will produce the following output −
{ "_id" : 2, "dueDate" : ISODate("2020-01-31T00:00:00Z") }
{ "_id" : 1, "dueDate" : ISODate("2019-01-10T00:00:00Z") }
Updated on: 30-Mar-2020
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