Loopback does not support group by or distinct query. But we can achieve in loopback another way. Let see a solution for this issue.

1. Distinct

// Let User is a Model and we want to get unique names

var collection = User.getDataSource().connector.collection(<Model_Name>);
collection.distinct( "name",
  function(err, records) {
    if(err) {
      return cb(err);
    } else {
      return cb(null, records);
    }
  });

distinct query with condition.

// Let User is a Model and we want to get unique names

var collection = User.getDataSource().connector.collection(<Model_Name>);
collection.distinct( "name", {name: {$ne:'abc'}}
  function(err, records) {
    if(err) {
      return cb(err);
    } else {
      return cb(null, records);
    }
  });

2. Using aggregation

var collection = User.getDataSource().connector.collection(<Model_Name>);
collection.aggregate(
 [
    { $match: { gender: 'female' } },
    { $group: { _id: $name} },
    { $project: { name:$_id, _id:0 } }
],
  function(err, records) {
    if(err) {
      return cb(err);
    } else {
      return cb(null, records);
    }
  });