mongodb null code example

Example 1: mongodb exists and not null

db.collection1.find({ 'fieldname1' : { $exists: true, $ne: null } });

Example 2: mongodb query missing field

db.inventory.find( { item: null } )

Example 3: mongodb find all that dont have property

db.things.find( { a : { $exists : false } } ); // return if a is missing