Query distinct not null values in MongoDb

Question

I'm just beginning to learn MongoDb and am having some problems with distinct queries.

If I for instance run the query

db.images.distinct('gallery') 

I get the expected result, but also empty strings and null values. How can I write a query that just returns the values that are not null?

Thanks

Answer 1

to avoid only null values use $ne

db.images.distinct( "gallery" , { "gallery" : { $ne : null } } );

or avoid "",null and more by specifying in an array using $nin.

db.images.distinct( "gallery" , { "gallery" : { $nin : ["", null] } });