Oracle 11g Release 2

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create table myprojects ( startdate date, enddate date, profit  number);        
insert into myprojects (startdate, enddate,profit ) 
values(to_date('1/5/2019','mm/dd/yyyy'),to_date('5/1/2019','mm/dd/yyyy'),100);   
    
1 rows affected

insert into myprojects (startdate, enddate,profit ) 
values(to_date('1/6/2019','mm/dd/yyyy'),to_date('2/10/2019','mm/dd/yyyy'),50);   
  
1 rows affected

alter table myprojects add ( projectid number ); 
select * from myprojects;


STARTDATE
ENDDATE
PROFIT
PROJECTID


05-JAN-19
01-MAY-19
100
null

06-JAN-19
10-FEB-19
50
null


update myprojects p
   set projectid = ( with t as ( 
                         select m.*,
                                row_number() 
                                over (order by startdate, enddate, profit) as rn
                           from myprojects m
                    )  
                    select rn
                      from t
                     where t.startdate = p.startdate
                       and t.enddate = p.enddate
                       and t.profit = p.profit
                     ); 
2 rows affected

select * from myprojects;


STARTDATE
ENDDATE
PROFIT
PROJECTID


05-JAN-19
01-MAY-19
100
1

06-JAN-19
10-FEB-19
50
2