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Oracle® Database SQL Language Reference
11g Release 1 (11.1)

Part Number B28286-01
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Description of group_id.gif follows
Description of the illustration group_id.gif


GROUP_ID distinguishes duplicate groups resulting from a GROUP BY specification. It is useful in filtering out duplicate groupings from the query result. It returns an Oracle NUMBER to uniquely identify duplicate groups. This function is applicable only in a SELECT statement that contains a GROUP BY clause.

If n duplicates exist for a particular grouping, then GROUP_ID returns numbers in the range 0 to n-1.


The following example assigns the value 1 to the duplicate co.country_region grouping from a query on the sample tables sh.countries and sh.sales:

SELECT co.country_region, co.country_subregion,
   SUM(s.amount_sold) "Revenue",
   GROUP_ID() g
FROM sales s, customers c, countries co
WHERE s.cust_id = c.cust_id AND
   c.country_id = co.country_id AND
   s.time_id = '1-JAN-00' AND
   co.country_region IN ('Americas', 'Europe')
GROUP BY co.country_region,
   ROLLUP (co.country_region, co.country_subregion)
ORDER BY co.country_region, co.country_subregion, "Revenue", g;

COUNTRY_REGION       COUNTRY_SUBREGION                 Revenue          G
-------------------- ------------------------------ ---------- ----------
Americas             Northern America                    944.6          0
Americas                                                 944.6          0
Americas                                                 944.6          1
Europe               Western Europe                     566.39          0
Europe                                                  566.39          0
Europe                                                  566.39          1

To ensure that only rows with GROUP_ID < 1 are returned, add the following HAVING clause to the end of the statement :