Find documents where value is not null

Question

I have the following doc structure

{
    "model" : {

    },
    "_id" : ObjectId("538df963d1c3f82329000257"),
    "email" : "[email protected]",
    "name" : "sam",
    "endpointarn" : "arn:aws:sns:us-east-1:284585229836:endpoint/GCM/Positivethinking/59eb7c66-c13c-3e44-af80-0b1f4f7ea9fd",
    "devregidtoken" : "APA91bFMOBo6ZWemMAG5clKEd5VYVvbeDOM5zNXjbbl3faSE0FZt3gtJYv0hpjdWuOY-mvr-k3sCcq0dEveCM6jx5mOh1u6JEubuUmKb2zU64dn_A4gJ4pCBG7AGQJ8DnkO83Ca4wgzsoJcio9T-TtA",
    "topicsubs" : [
        {
            "topicsubid" : "arn:aws:sns:us-east-1:284585229836:Wealth-ProsperityQuotes:5f3e8060-48fa-4a8e-bdc3-e9596747da1a",
            "topicname" : "Wealth-Prosperity",
            "topicno" : 0
        }
    ],
    "timecreated" : ISODate("2014-06-03T16:35:47.442Z"),
    "purchasedata" : {
        "orderid" : "111",
        "packagename" : "",
        "productid" : "",
        "purchasetime" : "",
        "purchasestate" : "",
        "developerpayload" : "",
        "purchasetoken" : ""
    },
    "ccode" : "",
    "ccodestat" : ""
}

I want to get all documents where purchasedata.orderid IS NOT NULL. I have tried

db.User.find({"purchasedata.orderid" : {$ne : ""}});

Answer 1

If you're checking for null you can use $ne operator:

db.User.find({
   "purchasedata.orderid" : { $ne : null }
});

Note:

OP originally wanted to check that the value is not an empty string "" and not null. null and empty string are two different BSON types. You can use $type and $not operators to check where the value is null and that the key exists:

db.User.find({
   "purchasedata.orderid" : { 
      $not : { $type : 10 }, 
      $exists : true
   }
});

The $type operator selects documents where the value is a specific BSON type (10 corresponds to Null). $exists will check that the key exists in the subdocument.

Answer 2

You were very close. If the value is actually null, you can just use "null" instead of blank.

db.User.find({"purchasedata.orderid" : {$ne : null}});

Answer 3

So this is what finally worked for me

db.User.find({
   "purchasedata.orderid" : {
      $exists : true,
      $ne : ""
   }
});

@Christian p was close so I up voted, but I think my problem was the value wasn't null but actually a empty string, also checking if the value exists is important