CREATE TABLE sample_test_avik  
  (  
    PRODUCT_ID  NUMBER,  
    START_DATE  DATE,  
    END_DATE    DATE,  
    PRICE_VALUE NUMBER  
  )

 INSERT INTO sample_test_avik values (1, to_date('01-JAN-2015','DD-MON-YYYY'),to_date('04-JAN-2015','DD-MON-YYYY'), 100)

 INSERT INTO sample_test_avik values (1, to_date('05-JAN-2015','DD-MON-YYYY'),to_date('11-JAN-2015','DD-MON-YYYY'), 120)

 INSERT INTO sample_test_avik values (1, to_date('12-JAN-2015','DD-MON-YYYY'),to_date('20-JAN-2015','DD-MON-YYYY'), 100)

 INSERT INTO sample_test_avik values (1, to_date('21-JAN-2015','DD-MON-YYYY'),to_date('27-JAN-2015','DD-MON-YYYY'), 100)

 INSERT INTO sample_test_avik values (1, to_date('28-JAN-2015','DD-MON-YYYY'),to_date('15-FEB-2015','DD-MON-YYYY'), 120)

 INSERT INTO sample_test_avik values (1, to_date('16-FEB-2015','DD-MON-YYYY'),to_date('04-MAR-2015','DD-MON-YYYY'), 150)

 INSERT INTO sample_test_avik values (1, to_date('05-MAR-2015','DD-MON-YYYY'),to_date('13-MAR-2015','DD-MON-YYYY'), 150)

 INSERT INTO sample_test_avik values (1, to_date('14-MAR-2015','DD-MON-YYYY'),to_date('30-APR-2015','DD-MON-YYYY'), 150)

 INSERT INTO sample_test_avik values (1, to_date('01-MAY-2015','DD-MON-YYYY'),to_date('10-MAY-2015','DD-MON-YYYY'), 150)

 INSERT INTO sample_test_avik values (1, to_date('11-MAY-2015','DD-MON-YYYY'),to_date('25-MAY-2015','DD-MON-YYYY'), 200)

 INSERT INTO sample_test_avik values (1, to_date('26-MAY-2015','DD-MON-YYYY'),to_date('31-MAY-2015','DD-MON-YYYY'), 240)

 commit

select product_id, min(start_date), max(end_date) from ( 
  select a.*,  
         row_number() over (partition by price_value order by start_date) rn, 
         row_number() over (order by start_date) rk, 
         row_number() over (order by start_date) -  
           row_number() over (partition by price_value order by start_date) grp 
  from   sample_test_avik a 
) 
group  by product_id, price_value, grp 
order  by 2

select * from sample_test_avik 
match_recognize ( 
  partition by product_id 
  order by start_date 
  measures first(a.start_date) as st, 
           nvl(b.end_date, a.end_date) as ed 
  pattern (a b*) 
  define  
    b as b.price_value = prev(b.price_value) 
)