How can I combine records on the basis of some conditions - oracle

Question

I have following table,
id id_concept start_date end_date
----------------------------------------------
100 282 20/06/2016 24/06/2016
100 282 15/07/2016 18/07/2016
300 282 01/09/2016 02/09/2016
I need to combine the records which has same id,id_concept and the time between END_DATE of one record and START_DATE of the next is 30 days or less (<=30)
Also for the combined records, I need to take the start_date as the very first start_date of the record and end _date as the end_date of the last record
The o/p should be like,
id id_concept start_date end_date count
---------------------------------------------------
100 282 20/06/2016 18/07/2016 2
300 282 01/09/2016 02/09/2016 1

Answer 1

SQL Fiddle
PostgreSQL 9.3 Schema Setup:
CREATE TABLE table_name ( id, id_concept, start_date, end_date ) AS
SELECT 100, 282, DATE '2016-06-20', DATE '2016-06-24' UNION ALL
SELECT 100, 282, DATE '2016-07-15', DATE '2016-07-18' UNION ALL
SELECT 300, 282, DATE '2016-09-01', DATE '2016-09-02';
Query 1:
SELECT id,
id_concept,
MIN( start_date ) AS start_date,
MAX( end_date ) AS end_date,
COUNT(*) AS "count"
FROM (
SELECT id,
id_concept,
start_date,
end_date,
SUM( diff ) OVER (
PARTITION BY id, id_concept
ORDER BY start_date, end_date
) AS grp
FROM (
SELECT t.*,
CASE
WHEN LAG( end_date ) OVER (
PARTITION BY id, id_concept
ORDER BY start_date, end_date
) >= start_date - INTERVAL '30' DAY
THEN 0
ELSE 1
END AS diff
FROM table_name t
) t
) t
GROUP BY id, id_concept, grp
Results:
| id | id_concept | start_date | end_date | count |
|-----|------------|-----------------------------|-----------------------------|-------|
| 300 | 282 | September, 01 2016 00:00:00 | September, 02 2016 00:00:00 | 1 |
| 100 | 282 | June, 20 2016 00:00:00 | July, 18 2016 00:00:00 | 2 |