GROUPING_ID

Syntax

Description of the illustration grouping_id.gif

Purpose

GROUPING_ID returns a number corresponding to the GROUPING bit vector associated with a row. GROUPING_ID is applicable only in a SELECT statement that contains a GROUP BY extension, such as ROLLUP or CUBE, and a GROUPING function. In queries with many GROUP BY expressions, determining the GROUP BY level of a particular row requires many GROUPING functions, which leads to cumbersome SQL. GROUPING_ID is useful in these cases.

GROUPING_ID is functionally equivalent to taking the results of multiple GROUPING functions and concatenating them into a bit vector (a string of ones and zeros). By using GROUPING_ID you can avoid the need for multiple GROUPING functions and make row filtering conditions easier to express. Row filtering is easier with GROUPING_ID because the desired rows can be identified with a single condition of GROUPING_ID = n. The function is especially useful when storing multiple levels of aggregation in a single table.

Examples

The following example shows how to extract grouping IDs from a query of the sample table sh.sales:

SELECT channel_id, promo_id, sum(amount_sold) s_sales,
   GROUPING(channel_id) gc,
   GROUPING(promo_id) gp,
   GROUPING_ID(channel_id, promo_id) gcp,
   GROUPING_ID(promo_id, channel_id) gpc
   FROM sales
   WHERE promo_id > 496
   GROUP BY CUBE(channel_id, promo_id);
 
C   PROMO_ID    S_SALES         GC         GP        GCP        GPC
- ---------- ---------- ---------- ---------- ---------- ----------
C        497   26094.35          0          0          0          0
C        498    22272.4          0          0          0          0
C        499    19616.8          0          0          0          0
C       9999   87781668          0          0          0          0
C            87849651.6          0          1          1          2
I        497    50325.8          0          0          0          0
I        498    52215.4          0          0          0          0
I        499   58445.85          0          0          0          0
I       9999  169497409          0          0          0          0
I             169658396          0          1          1          2
P        497   31141.75          0          0          0          0
P        498    46942.8          0          0          0          0
P        499      24156          0          0          0          0
P       9999   70890248          0          0          0          0
P            70992488.6          0          1          1          2
S        497  110629.75          0          0          0          0
S        498   82937.25          0          0          0          0
S        499   80999.15          0          0          0          0
S       9999  267205791          0          0          0          0
S             267480357          0          1          1          2
T        497     8319.6          0          0          0          0
T        498    5347.65          0          0          0          0
T        499      19781          0          0          0          0
T       9999   28095689          0          0          0          0
T            28129137.3          0          1          1          2
         497  226511.25          1          0          2          1
         498   209715.5          1          0          2          1
         499   202998.8          1          0          2          1
        9999  623470805          1          0          2          1
              624110031          1          1          3          3