Difference between two rows in sql

Question

How to calculate difference between two rows in sql developer?? Scenario is Employee1 has two tasks so I need to calculate the difference between the start date of task1 and finish date of task2 And in 3rd row again Employee2 has two tasks so I need to calculate that difference too. Can someone help me in this please...

Answer 1

If I understand correctly, you want lag() :

select t.*,
       start_date - lag(end_date) over (partition by employee order by start_date) as diff
from t;