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
Find maximum score for duplicate Name values in MongoDB?
To find maximum score, use GROUP() to group documents in a collection. Let us create a collection with documents −
> db.demo114.insertOne({"Score":60,"Name":"Chris"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2efc57d8f64a552dae6354")
}
> db.demo114.insertOne({"Score":87,"Nam+e":"Chris"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2efc5ad8f64a552dae6355")
}
> db.demo114.insertOne({"Score":45,"Name":"David"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2efc5dd8f64a552dae6356")
}
> db.demo114.insertOne({"Score":67,"Name":"Chris"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2efc68d8f64a552dae6357")
}
> db.demo114.insertOne({"Score":38,"Name":"David"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2efc74d8f64a552dae6358")
}Display all documents from a collection with the help of find() method −
> db.demo114.find();
This will produce the following output −
{ "_id" : ObjectId("5e2efc57d8f64a552dae6354"), "Score" : 60, "Name" : "Chris" }
{ "_id" : ObjectId("5e2efc5ad8f64a552dae6355"), "Score" : 87, "Name" : "Chris" }
{ "_id" : ObjectId("5e2efc5dd8f64a552dae6356"), "Score" : 45, "Name" : "David" }
{ "_id" : ObjectId("5e2efc68d8f64a552dae6357"), "Score" : 67, "Name" : "Chris" }
{ "_id" : ObjectId("5e2efc74d8f64a552dae6358"), "Score" : 38, "Name" : "David" }Following is the query to find maximum. This calculates the maximum score of let’s say duplicate name values, such as “Chris” and “David” −
> db.demo114.group(
... {key: {Name:true},
... reduce: function(c,p) {
... if (p.maximumScore < c.Score) {
... p.maximumScore = c.Score;
... }
... },
... initial: { maximumScore: 0 }}
... );This will produce the following output −
[
{
"Name" : "Chris",
"maximumScore" : 87
},
{
"Name" : "David",
"maximumScore" : 45
}
]
Updated on: 30-Mar-2020
92 Views
Advertisements