The CrossTable class encapsulates a crosstab operation. Its two subclasses, ColumnCross and RowCross, represent differences in arrangements of the constructed rows. In both arrangements, the values displayed are usually aggregations, and the values in a specified database column determine the structure of the arrangement. In the ColumnCross style, the values stored in the specified column determine the column headers, whereas in the RowCross style, they determine the set of rows (one row for each value repeated for each row identifier).