- Trending Categories
Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
How to sort by the difference in array contents in MongoDB?
To sort by difference, use aggregate() in MongoDB. Let us create a collection with documents −
> db.demo155.insertOne({"Scores":[{"Value":45},{"Value":50}]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e354584fdf09dd6d08539e3")
}
> db.demo155.insertOne({"Scores":[{"Value":60},{"Value":10}]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e35458efdf09dd6d08539e4")
}
> db.demo155.insertOne({"Scores":[{"Value":100},{"Value":95}]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e354599fdf09dd6d08539e5")
}
Display all documents from a collection with the help of find() method −
> db.demo155.find();
This will produce the following output −
{ "_id" : ObjectId("5e354584fdf09dd6d08539e3"), "Scores" : [ { "Value" : 45 }, { "Value" : 50 } ] }
{ "_id" : ObjectId("5e35458efdf09dd6d08539e4"), "Scores" : [ { "Value" : 60 }, { "Value" : 10 } ] }
{ "_id" : ObjectId("5e354599fdf09dd6d08539e5"), "Scores" : [ { "Value" : 100 }, { "Value" : 95 } ] }
Following is the query to sort by the difference in array contents with MongoDB −
> db.demo155.aggregate([
... { "$match": { "Scores.1": { "$exists": true } } },
... { "$project": {
... "Scores": "$Scores",
... "sub": {
... "$let": {
... "vars": {
... "f": { "$arrayElemAt": [ "$Scores", -2 ] },
... "l": { "$arrayElemAt": [ "$Scores", -1 ] }
... },
... "in": { "$subtract": [ "$$l.Value", "$$f.Value" ] }
... }
... }
... }},
... { "$sort": { "sub": -1 } }
... ])
This will produce the following output −
{ "_id" : ObjectId("5e354584fdf09dd6d08539e3"), "Scores" : [ { "Value" : 45 }, { "Value" : 50 } ], "sub" : 5 }
{ "_id" : ObjectId("5e354599fdf09dd6d08539e5"), "Scores" : [ { "Value" : 100 }, { "Value" : 95 } ], "sub" : -5 }
{ "_id" : ObjectId("5e35458efdf09dd6d08539e4"), "Scores" : [ { "Value" : 60 }, { "Value" : 10 } ], "sub" : -50 }
Updated on: 2020-04-01T11:33:27+05:30
192 Views
Advertisements