how to do this query in mongoDB?

Question

How do I make this query in mongoDB?

{

_id: "*******"

content: "",

comments: [

{

key1: "1",

key2: "2"

},

{

key1: "sdfs",

key2: "sdfasdf"

}

]

}

For example, I use the data as below. I want to query the items in comments in condition {key1: 1, key2: 2}, and not return the whole record.

What should I do?

score 3 · Answer 1 · answered Jun 26 '12 at 08:24

3

You can try to this one

{ "comments.key1" : "1", "comments.key2" : "sdfasdf" }

You only need to use this when more than one field must be matched in the array element.

answered Jun 26 '12 at 08:24

turankonan

1

That won't work. This will match even if one comments has key1, and a *different* comment has key2. You need to use $elemMatch. – Thilo Jun 27 '12 at 00:12

score 1 · Answer 2 · edited May 23 '17 at 12:20

1

You can query a subdocument on two fields using $elemMatch:

{ comments: { $elemMatch : { key1: 1, key2: 2 } } }

You cannot return just the selected subdocument. You'll get all of them. So you'll have to filter on the client side. (You can of course, exclude all other fields of the main document).

edited May 23 '17 at 12:20

Community

answered Jun 26 '12 at 02:09

Thilo

1

you mean even I use "$elemMatch", two subdocuments will still return ? – edge_man Jun 26 '12 at 02:13
`$elemMatch`! I did not know about that. Yes, that would work. Updating answer. – Thilo Jun 26 '12 at 02:17

2 Answers2