GROUPING_ID
Syntax
grouping_id::=
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
