What is true of using group functions on columns that contain NULL values?
A.
Group functions on columns ignore NULL values.
B.
Group functions on columns returning dates include NULL values.
C.
Group functions on columns returning numbers include NULL values.
D.
Group functions on columns cannot be accurately used on columns that contain NULL values.
E.
Group functions on columns include NULL values in calculations if you use the keyword
INC_NULLS.
Explanation:
group functions on column ignore NULL values
Incorrect answer:
Bgroup functions on column ignore NULL values
Cgroup functions on column ignore NULL values
DNVL function can be use for column with NULL values
Eno such INC_NULLS keyword
Refer: Introduction to Oracle9i: SQL, Oracle University Study Guide, 5-12
What about option C ?? Need Help.
From documentation:
“All aggregate functions except COUNT(*), GROUPING, and GROUPING_ID ignore nulls.”
http://docs.oracle.com/cd/E11882_01/server.112/e26088/functions003.htm
Can anyone pls provide a reference/link which proves optn C wrong.
WITH x AS (SELECT 1 a FROM DUAL
UNION
SELECT NULL FROM DUAL)
SELECT SUM (a), COUNT (a)
FROM x
@jb, very nice example.
@All
Rows with NULLs occurring in columns or expressions are ignored by all group functions, except
– COUNT(some literal)
– AVG(some literal)
– SUM(some literal)