How to choose one document from the set?

Question

MongoDB

Marvel.create({name: 'Superman', type: 'superhero'});
Marvel.create({name: 'Superman', type: 'superhero'});
Marvel.create({name: 'Batman', type: 'superhero'});
Marvel.create({name: 'Batman', type: 'superhero'});
Marvel.create({name: 'Joker', type: 'supervillain'});
Marvel.create({name: 'Superman', type: 'supervillain'});

How to write a query in mongoose to get -

[
    {name: 'Superman', type: 'superhero'},
    {name: 'Batman', type: 'superhero'}
]

Answer 1

Marvel.aggregate( [
  {$group: {_id : {name : '$name', type:'$type'}}},
  {$project : {name: '$_id.name', type: '$_id.type', _id : 0}}
], function (err, result) {
        if (err) {
            console.log(err);
        } else {
            console.log(result);
        }
    });