Oracle update query to update records in sequential order

Question

I have a table in Oracle SQL whose ids are in increasing, sequential order, but there are gaps in the ids due to editing, e.g. the ids are currently something like

Answer 1

You could use a merge, but you'd need to join on something other than emp_id as you want to update that column. If there are no other unique columns you can use the rowid:

merge into employee target
using (select rowid, row_number() over (order by emp_id) as emp_id from employee) source
on (source.rowid = target.rowid)
when matched then update set target.emp_id = source.emp_id;