Mongo DB add new value to array

Question

I need to add a value to mongo db inner object with array element without looking at other value. Can some one advice to do this.

Eg: take order collection as,

{_id:'ssdeiieirei33',userId: 213828, enrolLment:{"ADMIN":{"TERM1":["COURSE1","COURSE3"]},"STUD":{"TERM2":["COURSE1","COURSE2"]}}}

Here I need to add new enrollment(COURSE3) (STUD:{"TERM2":["COURSE3"]}) to enrolLment column with out reading it . this should be the result;

 {_id:'ssdeiieirei33',userId: 213828, enrolLment:{"ADMIN":{"TERM1":["COURSE1","COURSE3"]},"STUD":{"TERM2":["COURSE1","COURSE2","COURSE3"]}}}

Is it possible?

Yes, you are looking for the $push operator (or alternatively $addToSet when you want to avoid duplicates) — Philipp
– Philipp, Commented Sep 28, 2015 at 11:13
I updated the question with my real collection. sorry about inconvenience — Dinusha
– Dinusha, Commented Sep 28, 2015 at 12:38

Pio · Accepted Answer · 2015-09-28 12:50:39Z

1

Depending on your needs you can use $addToSet if you don't want duplicates or $push if duplicates are allowed.

From your wording it seems to me that you want to use $addToSet, but please clarify.

UPDATE

You should use

collection.update({condition},
    {
        $addToSet: {enrolLment.$userName.$Term : "COURSE3"}
    },
callback)

Note that I did not test my code. enrolLment.$userName.$Term in your case should be enrolLment.ADMIN.TERM2. But if you have them in the condition then you can use the $ notation to access those variables.

edited Sep 28, 2015 at 12:50

answered Sep 28, 2015 at 11:12

Pio

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2 Comments

Pio Over a year ago

As @JohnnyHK said, your question is not really valid. Do you want to have only counts of items? Then use {..., items: {'pen':3, 'book':4}}. That way you don't need any arrays, since you basically have a hash-map.

Dinusha Over a year ago

I updated the question with my real collection. sorry about inconvenience

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