count method
count count of all num column
Implementation
@override
Future<int?> count([String column = '*']) async {
final builder = _copyQueryWith(columns: ['COUNT($column)']);
final completer = Completer<List<Map<String, dynamic>>>()
..complete(database!.rawQuery(builder.sql, builder.arguments));
if (isLogger!) Logger.query(type, completer.future, builder);
final result = await completer.future;
return result.firstOrNull?.values.firstOrNull as int?;
}