One or more numerical columns in a table are aggregated using no, one or several dimension columns. In all rows that have the same values in all dimension columns, the values in the columns to be aggregated are combined into one row based on an aggregation rule, i.e., the result contains one row for each combination of dimension columns. This also applies if no columns are specified for aggregation. If no dimension column is specified, only a single row is created and all values in the columns to be aggregated are combined to a single value for each column. No rows are created for combinations that do not occur in the original table.