Update expired records

I have a records loaded from a tool into a table as follows. The audit columns start_dt and end_dt and valid_fl is not loaded if the multiple records exists for the same empid. But after initial the audit column value is inserted properly. I am trying to come up with a script to update the audit columns after intitial load as followsas follows

empid   salary_rt   eff_dt                  start_dt               end_dt                                     valid fl

100       abc          10/05/2014         10/05/2014       06/04/2015                             N
100       lmn          06/04/2015         06/04/2015       05/10/2019                             N
100       pqr           05/10/2019         05/10/2019       12/31/9999 (Future date)     Y
200       lkd           04/02/2018          04/02/2018      05/20/2019                             N
200       fjk            05/20/2019          05/20/2019      12/31/9999 (Future date)      Y

Is there a way to do it in plsql?

Thanks