How to write the SQL for the following

Question

ID     PRODUCT     LEAD_FLAG     SALES_VOLUME
1     A     Y     100
1     B     N     200
1     C     N     300
1     D     N     400
2     A     N     10
2     B     Y     20
2     C     N     30
2     D     N     40
I need to calculate the incentive for each ID. The rule is for an ID:
if the the lead flag for a product is N, then check the sales_volume of the product whose lead_flag is Y (product A in case of ID 1, product B in case of ID 2). if the sales_volume of the product with lead_flag = Y is greater than a NUMBER (this NUMBER varies from product to product. for product A it is 20, for product B it is 25, C it is 30 and D it is 40) then incentive = (sales_volume of the product with lead flag N) * 100.

Answer 1

Hello, I presume the NUMBER you refer to will be held in a table column somewhere? I'm calling it threshold_num in the test data below (and rec_id instead of ID):
WITH test_data AS (
SELECT 1 REC_ID, 'A' PRODUCT, 'Y' LEAD_FLAG,  100 SALES_VOLUME FROM DUAL UNION ALL
SELECT 1, 'B','N', 200 FROM DUAL UNION ALL
SELECT 1, 'C','N', 300 FROM DUAL UNION ALL
SELECT 1, 'D','N', 400 FROM DUAL UNION ALL
SELECT 2, 'A','N', 10 FROM DUAL UNION ALL
SELECT 2, 'B','Y', 20 FROM DUAL UNION ALL
SELECT 2, 'C','N', 30 FROM DUAL UNION ALL
SELECT 2, 'D','N', 40 FROM DUAL),
test_ref_data AS (
SELECT 'A' PRODUCT, 20 threshold_num FROM DUAL UNION ALL
SELECT 'B', 25 FROM DUAL UNION ALL
SELECT 'C', 30 FROM DUAL UNION ALL
SELECT 'D', 40 FROM DUAL)
-- end test data
SELECT td1.REC_ID, td1.PRODUCT, CASE WHEN td2.PRODUCT IS NOT NULL THEN td1.sales_volume * 100 ELSE 0 END incentive
  FROM test_data td1
   LEFT JOIN (
    SELECT td2.PRODUCT, SUM(sales_volume) sales_volume
     FROM test_data td2
     JOIN test_ref_data trd
        ON (td2.PRODUCT = trd.PRODUCT)
   WHERE td2.lead_flag = 'Y'
    GROUP BY td2.PRODUCT, trd.threshold_num HAVING SUM(td2.sales_volume) > trd.threshold_num) td2
    ON (td1.PRODUCT = td2.PRODUCT)
WHERE td1.lead_flag = 'N';
    REC_ID PROD  INCENTIVE
         2 A       1000
         2 D          0
         1 D          0
         1 B          0
         2 C          0
         1 C          0
6 rows selected.And two tips: it's always helps to put {noformat}{noformat} before and after your code for readability, and also to provide expected sample output.