Checking using nvl2 with multiple group by - sql

Question

I have a table like
------------------------
S.No Name Amount Imp_Num
1 A 10 12345
2 B 20
3 A 30
4 C 40 4555
5 B 50
--------------------------
and I want something like
---------------------------------------
Name Total_Amount Imp_Num Imp_Num_Present
A 40 12345 Y
B 70 null N
C 40 4555 Y
---------------------------------------
The important_number_present column should be Y if the important number is present for the particular name at least once and the important number should be captured. The important number for a particular name is assumed to be the same.If different the latest one should be displayed as imp_numb. (But this is of secondary priority).
I tried something like
Select sum(amount) as total_amount, imp_num, nvl2(imp_num,'Y','N') from sampletable group by imp_num;
But name can't be retrieved and the data doesn't make sense without the name. I might be doing something totally wrong. Can a feasible solution be done in SQL rather than in pl/sql.
Group by with name is returning the name with a null entry and imp_num entry.
I am cracking my head on this. Would be of great help, if someone solves it.
Thanks in advance

Answer 1

You could use a (fake) aggregation function on imp_num and group by name
Select Name, sum(amount) as total_amount, max(imp_num), nvl2( max(imp_num),'Y','N')
from sampletable
group by Name;

Answer 2

EDIT: Another solution with COUNT function. DEMO
SELECT name
,SUM(amount) AS total_amount
,MAX(imp_num) AS Imp_Num
,CASE
WHEN Count(imp_num) > 0
THEN 'Y'
ELSE 'N'
END AS Imp_Num_Present
FROM yourtable
GROUP BY name
You may also use a MAX( CASE ) block
SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE yourtable
(S_No int, Name varchar2(1), Amount int, Imp_Num varchar2(5))
;
INSERT ALL
INTO yourtable (S_No, Name, Amount, Imp_Num)
VALUES (1, 'A', 10, '12345')
INTO yourtable (S_No, Name, Amount, Imp_Num)
VALUES (2, 'B', 20, NULL)
INTO yourtable (S_No, Name, Amount, Imp_Num)
VALUES (3, 'A', 30, NULL)
INTO yourtable (S_No, Name, Amount, Imp_Num)
VALUES (4, 'C', 40, '4555')
INTO yourtable (S_No, Name, Amount, Imp_Num)
VALUES (5, 'B', 50, NULL)
SELECT * FROM dual
;
Query 1:
SELECT Name,
SUM (amount) AS total_amount,
MAX (imp_num) AS Imp_Num,
CASE
WHEN MAX (CASE WHEN imp_num IS NOT NULL THEN 1 ELSE 0 END) = 1
THEN
'Y'
ELSE
'N'
END
AS Imp_Num_Present
FROM yourtable
GROUP BY Name
Results:
| NAME | TOTAL_AMOUNT | IMP_NUM | IMP_NUM_PRESENT |
|------|--------------|---------|-----------------|
| A | 40 | 12345 | Y |
| B | 70 | (null) | N |
| C | 40 | 4555 | Y |