private void comboBoxExamples_SelectedIndexChanged(object sender, EventArgs e)
        {
            _query.Clear();

            // HOWTO: Create a query programmatically
            switch (comboBoxExamples.SelectedIndex)
            {
            case 0:
                LoadQuerySimple();
                break;

            case 1:
                LoadQueryWithLeftJoin();
                break;

            case 2:
                LoadQueryWithAggregateAndGroup();
                break;

            case 3:
                LoadQueryWithDerivedTableAndCte();
                break;

            case 4:
                LoadQueryWithUnions();
                break;

            case 5:
                LoadQueryWithSubQueryExpression();
                break;

            default:
                throw new ArgumentOutOfRangeException();
            }
        }