MongoDB: How to query nested array specific elements? - mongodb

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"
},
..........
..........
..........
..........
}
}

Answer 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.

Answer 2

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.