Useful documentation

From MongoDB

• Dot Notation
• Updating
• Removing

Querying

Querying field of embedded document in an array

Just use the dot syntax, here’s an example from Dot Notation

> db.blogposts.findOne()
{ title : "My First Post", author: "Jane",
  comments : [{ by: "Abe", text: "First" },
              { by : "Ada", text : "Good post" } ]
}
> db.blogposts.find( { "comments.by" : "Ada" } )

Find non null field

db.collection.find( { 'field': { '$ne' : null } } )