SQL Query Oracle: Two date columns on same table for different rows

Question

For CallLogTable....I need to write a query which finds scenarios where the created_ts timestamp of one row has an earlier timestamp than the updated_ts timestamp of the row immediately BEFORE. Rows 1 and 2 are an example (The created_ts of row 2 is earlier than the updated_ts of row 1). I have seen use of Rownums but not sure how to apply it here. Many thanks in advance for your help!

Answer 1

You can use window functions. lag() lets you access the previous row, and you can then compare the relevant columns:

select *
from (
    select  
        t.*,
        lag(updated_ts) over(order by id) lag_updated_ts
    from mytable t
) t
where created_ts < lag_updated_ts

This assumes that column id can be used to order the records. If you want a different column for ordering, then you can change the order by clause of the window function.