In PL/SQL, how do you update a row based on the next row?

Question

I\'m using Oracle PL/SQL.

I have a timestamped table T, and I want to set a row\'s value for column A to be the same as that of the previous row, if they\'re sorted

Answer 1

Try using a merge statement. Not sure it quite does what you want but it should work. Unfortunately the insert clause is necessary) but shouldn't ever be called.

merge into t a
using (
  select 
    A, 
    B, 
    timestamp, 
    lag(A) over (order by id, timestamp) as prior_A,
    lag(timestamp) over (order by B, timestamp) as prior_timestamp
  from t) b
on  (a.B = b.B)
when matched then 
  update set a.a = case when b.timestamp-b.prior_timestamp <= 45 
    then b.prior_A else b.A end
when not matched then insert (B) values (null)