MongoDB: How to query nested array specific elements?

Question

I've a complex collection in MongoDB. In this, I want to query departments data based on the subDeptName. I used query like below db.getCollection('users').find({"departments.subDeptName" : "Java"}), but its fetching all the array elements of the department. I only wants to query such department where "subDeptName" : "Java". How can we do that ?

{
    "firstName" : "John",
    "lastName" : "Kerr",
    "email" : "john.kerr@gmail.com",
    "countryName" : "USA",
    "usRestrictionSw" : "N",
    "status" : "Active",
    "effDate" : ISODate("2012-08-24T01:46:33.000Z"),
    "departments" : [ 
        {
            "subDeptCd" : "AB",
            "languageCd" : "en",
            "desc" : "Development Group",
            "subDeptName" : "Java",
            "status" : "Active"
        }, 
        {
            "subDivisionAlpha2Cd" : "KG",
            "subDivisionCd" : "B",
            "languageCd" : "ru",
            "desc" : "Testing Group",
            "subDeptName" : "Python",
            "status" : "Active"
        }, 
        ..........
        ..........
        ..........
        ..........
    }
}

Possible duplicate of [Retrieve only the queried element in an object array in MongoDB collection](https://stackoverflow.com/questions/3985214/retrieve-only-the-queried-element-in-an-object-array-in-mongodb-collection) — Ashh, May 10 '19 at 10:08

score 1 · Accepted Answer · answered May 10 '19 at 10:09

1

db.getCollection('users').find({"departments.subDeptName" : "Java"})

Will match all users with a sub deperament java.

Easiest way to achieve the result you want is this:

 db.getCollection('users').aggregate([
           {
             $unwind: "$departments"
           },
           { 
             $match: {
                "departments.subDeptName" : "Java"
           }
 ])

Now you can also add a $project phase to get only the specific fields you want.

answered May 10 '19 at 10:09

Tom Slabbaert

21,288
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Thanks ! But How can we query this using Spring Data Mongo APIs? – PAA May 10 '19 at 10:10
Is there any way if we can get the count of this fetch elements as well ? – PAA May 10 '19 at 10:16
sorry but what do you mean by "count"? the amount of documents returned is also the count (?). – Tom Slabbaert May 10 '19 at 10:18
I mean, Count of departments too – PAA May 10 '19 at 10:18
Could you please suggest that option too in your code ? – PAA May 10 '19 at 10:22

Amarat · Answer 2 · 2019-05-10T12:00:13.883

-1

Try this:-

db.getCollection('users').find({"departments.subDeptName" : "Java"})

i have checked this on command line work fine. Please check your mongo version and mongo shell version

mongod --version (check mongo version)

mongo --version // check mongo shell version.

And also check error log for have unother issue.

edited May 10 '19 at 12:00

answered May 10 '19 at 10:11

Amarat

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You did not followed my question, its pulling all the department array values – PAA May 10 '19 at 10:14
You use aggregate or not ? – Amarat May 10 '19 at 10:21

MongoDB: How to query nested array specific elements?

2 Answers2