avg method
AVG aggregate
Implementation
Future<double?> avg(String column) async {
final originalSelects = List<String>.from(_selects);
_selects.clear();
_selects.add('AVG($column) as avg_value');
final result = await first();
_selects.clear();
_selects.addAll(originalSelects);
return result?['avg_value']?.toDouble();
}