Top n Percent Equivalent

Question

Hello All,
I would like to know what is the equivalent of Top n Percent in Oracle sql 11g.
Here is my requirement:
I have to find stores contributing top 20% of sales:
Store
Sales
Percetage
ABC
200
(200/380)*100=52%
XYZ
100
(100/380)*100=26%
PQR
50
(50/380)*100=13%
dddd
20
(20/380)*100=5%
rrrr
10
(10/380)*100=2%
In the above example I have to get only store ABC as this store alone is contributing more than Top 20%
If I change the requirement to Top 70% I have to get store's ABC and XYZ.
Any help would be highly appreciated.
Thanks,
MC

Answer 1

Hi,
You can do that with analytic functions.
Since I don't have a test version of your table, I'll use the scott.emp table to illustrate
WITH got_totals AS
    SELECT    ename
    ,         sal
    ,         SUM (sal) OVER ( ORDER BY       sal DESC
                               RANGE BETWEEN  UNBOUNDED PRECEDING
                                     AND      1E-9      PRECEDING  -- arbitrary small number
                             ) AS running_total
    ,         SUM (sal) OVER ()            AS grand_total
    FROM      scott.emp
SELECT   ename
,        sal
FROM     got_totals
WHERE    NVL ( running_total
             , 0
             ) / grand_total   < .2     -- .2 means 20%
ORDER BY  sal DESC
With .2 in the WHERE clause, this produces the following output
ENAME             SAL GRAND_TOTAL RUNNING_TOTAL
KING             5000       29025
FORD             3000       29025          5000
SCOTT            3000       29025          5000
If you change the number in the WHERE clause to .1, you'll get KING alone, since KING's sal by itself accounts for more than 10% of the grand total (29025).
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for your table, and the query above as adapted for your table.
Point out where that query is producing the wrong results, and explain, using specific examples, how you get the right results from the given data in those places.
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