How to search in array of object in mongodb

Question

Suppose the mongodb document(table) 'users' is

{
    _id: 1,
    name: {
        first: 'John',
        last: 'Backus'
    },
    birth: new Date('Dec 03, 1924'),
    death: new Date('Mar 17, 2007'),
    contribs: ['Fortran', 'ALGOL', 'Backus-Naur Form', 'FP'],
    awards: [
        {
            award: 'National Medal',
            year: 1975,
            by: 'NSF'
        },
        {
            award: 'Turing Award',
            year: 1977,
            by: 'ACM'
        }
    ]
}
// ...and other object(person)s

I want to find the person who has the award 'National Medal' and must be awarded in year 1975 There could be other persons who have this award in different years.

How can I find this person using award type and year. So I can get exact person.

score 576 · Accepted Answer · edited Aug 06 '21 at 07:48

576

The right way is:

db.users.find({awards: {$elemMatch: {award:'National Medal', year:1975}}})

$elemMatch allows you to match more than one component within the same array element.

Without $elemMatch mongo will look for users with National Medal in some year and some award in the year 1975, but not for users with National Medal in 1975.

See MongoDB $elemMatch Documentation for more info. See Read Operations Documentation for more information about querying documents with arrays.

edited Aug 06 '21 at 07:48

kookaburra

3
3

answered Dec 26 '12 at 15:00

Leonid Beschastny

50,364
10
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7

i.e. elemMatch matches award 'and' year (as opposed to award 'or' year) – Aditya Mittal Aug 28 '18 at 19:20
how do we query only those documents that has first name as John and award as national medal in simple way? we do it with aggregate and iterating through awards array but wanted to know simple query – Venkatesh Kolla - user2742897 Jun 06 '19 at 10:02
if year would be an array of strings, how would the query look like? – Gobliins Sep 20 '21 at 17:03
@Gobliins the same, except year would be a string – Leonid Beschastny Sep 20 '21 at 18:14

score 33 · Answer 2 · edited May 31 '21 at 14:51

33

Use $elemMatch to find the array of a particular object

db.users.findOne({"_id": id},{awards: {$elemMatch: {award:'Turing Award', year:1977}}})

edited May 31 '21 at 14:51

turivishal

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answered Apr 28 '17 at 06:09

KARTHIKEYAN.A

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passing two objects to findOne, is this essentially a "subquery"? IE, we find the _ID = ID then search inside of that using $elemMatch? – Native Coder Sep 16 '20 at 23:41

Mohammad Yaser Ahmadi · Answer 3 · 2021-06-10T11:53:44.490

as explained in above answers Also, to return only one field from the entire array you can use projection into find. and use $

db.getCollection("sizer").find(
  { awards: { $elemMatch: { award: "National Medal", year: 1975 } } },
  { "awards.$": 1, name: 1 }
);

will be return

{
    _id: 1,
    name: {
        first: 'John',
        last: 'Backus'
    },
    awards: [
        {
            award: 'National Medal',
            year: 1975,
            by: 'NSF'
        }
    ]
}

score 11 · Answer 4 · edited Aug 28 '20 at 15:35

11

You can do this in two ways:

ElementMatch - $elemMatch (as explained in above answers)

db.users.find({ awards: { $elemMatch: {award:'Turing Award', year:1977} } })
Use $and with find

db.getCollection('users').find({"$and":[{"awards.award":"Turing Award"},{"awards.year":1977}]})

edited Aug 28 '20 at 15:35

alistair

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answered Jun 11 '20 at 09:44

Joby Wilson Mathews

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score 0 · Answer 5 · answered Feb 12 '23 at 04:06

0

Use $elemMatch to find the array of a particular object doc: https://www.mongodb.com/docs/manual/reference/operator/query/elemMatch/

answered Feb 12 '23 at 04:06

khoa junior

69
3

How to search in array of object in mongodb

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