In addition to the regular aggregation results we expect from the GROUP BY clause, the ROLLUP extension produces group subtotals from right to left and a grand total. If "n" is the number of columns listed in the ROLLUP, there will be n+1 levels of subtotals.

In addition to the subtotals generated by the ROLLUP extension, the CUBE extension will generate subtotals for all combinations of the dimensions specified. If "n" is the number of columns listed in the CUBE, there will be 2n subtotal combinations.

SELECT fact_1_id,
       fact_2_id,
       SUM(sales_value) AS sales_value
FROM   dimension_tab
GROUP BY ROLLUP (fact_1_id, fact_2_id)
ORDER BY fact_1_id, fact_2_id;

 FACT_1_ID  FACT_2_ID SALES_VALUE
---------- ---------- -----------
         1          1     4363.55
         1          2     4794.76
         1          3     4718.25
         1          4     5387.45
         1          5     5027.34
         1               24291.35
         2          1     5652.84
         2          2     4583.02
         2          3     5555.77
         2          4     5936.67
         2          5     4508.74
         2               26237.04
                         50528.39

SELECT fact_1_id,
       fact_2_id,
       fact_3_id,
       SUM(sales_value) AS sales_value
FROM   dimension_tab
GROUP BY ROLLUP (fact_1_id, fact_2_id, fact_3_id)
ORDER BY fact_1_id, fact_2_id, fact_3_id;

SELECT fact_1_id,
       fact_2_id,
       fact_3_id,
       SUM(sales_value) AS sales_value
FROM   dimension_tab
GROUP BY fact_1_id, ROLLUP (fact_2_id, fact_3_id)
ORDER BY fact_1_id, fact_2_id, fact_3_id;
							
SELECT fact_1_id,
       fact_2_id,
       SUM(sales_value) AS sales_value
FROM   dimension_tab
GROUP BY CUBE (fact_1_id, fact_2_id)
ORDER BY fact_1_id, fact_2_id;

 FACT_1_ID  FACT_2_ID SALES_VALUE
---------- ---------- -----------
         1          1     4363.55
         1          2     4794.76
         1          3     4718.25
         1          4     5387.45
         1          5     5027.34
         1               24291.35
         2          1     5652.84
         2          2     4583.02
         2          3     5555.77
         2          4     5936.67
         2          5     4508.74
         2               26237.04
                    1    10016.39
                    2     9377.78
                    3    10274.02
                    4    11324.12
                    5     9536.08
                         50528.39