Question

I need to retrieve documents that contain at least one value inside an array. The structure of my document is:

{ "_id": 3, 
"username": "111111", 
"name": "XPTO 1", 
"codes": [ 2, 4, 5 ], 
"available": true }


{ "_id": 4, 
"username": "22222", 
"name": "XPTO 2", 
"codes": [ 3, 5 ], 
"available": true }

I need to do a find by “codes” and if i search for value “5”, i need to retrieve all documents that contains this value inside their array.

I’ve tried to use #elemMatch but no success…

db.user.find({codes: {"$elemMatch": {codes: [2,8]}}}, {"codes":1})

How can i do this?

Thanks in advance.

Answer 1

You can check for values inside an array just like you compare the values for some field.
So, you would need to do it like this, without using $elemMatch: –

1. If you want to check whether an array contain a single value 5: –

   db.user.find({codes: 5}, {codes:1})
   

   This will return all the document, where codes array contain 5.

2. If you want to check whether an array contain a value out of given set of values: –

   db.user.find({codes: {$in: [2, 8]}}, {codes:1})
   

   This will return documents with array containing either 2 or 8

3. If you want to check whether an array contain all the values in a list: –

   db.user.find({codes: {$all: [2, 5]}}, {codes:1})
   

   This will return all document with array containing both 2 and 5.