Which two statements are true about the GROUPING function? (Choose two.)
A.
It is used to find the groups forming the subtotal in a row.
B.
It can only be used with ROLLUP and CUBE operators specified in the GROUP BY
clause.
C.
It is used to identify the NULL value in the aggregate functions.
D.
It is used to form the group sets involved in generating the totals and subtotals.
“GROUPING function returns “1” if the column contains a null value generated as part of a subtotal by a ROLLUP or CUBE operation or “0” for any other value, including stored null values.”
or
“Using the GROUPING function, you can distinguish a null representing the set of all values in a superaggregate row from a null in a regular row.”
http://www.aiotestking.com/oracle/which-two-statements-are-true-about-the-grouping-function-3/