Time Difference between query result rows in SQLite: How To?

Question

Consider the following reviews table contents:

CustomerName    ReviewDT
Doe,John        2011-06-20 10:13:24
Doe,John        2011-06-20 10:54:45
Doe,         


        

Answer 1

To compute the seconds elapsed from one ReviewDT row to the next:

 SELECT q.CustomerName, q.ReviewDT,
   strftime('%s',q.ReviewDT) 
   - strftime('%s',coalesce((select r.ReviewDT from Reviews as r
                       where r.CustomerName = q.CustomerName
                       and r.ReviewDT < q.ReviewDT
                       order by r.ReviewDT DESC limit 1), 
                       q.ReviewDT))
  FROM Reviews as q WHERE q.CustomerName NOT NULL 
  ORDER BY q.CustomerName ASC, q.ReviewDT ASC;

To get the DT of each ReviewDT and its preceding CustomerName row:

SELECT q.CustomerName, q.ReviewDT,
  coalesce((select r.ReviewDT from Reviews as r
                      where r.CustomerName = q.CustomerName
                      and r.ReviewDT < q.ReviewDT
                      order by r.ReviewDT DESC limit 1), 
                      q.ReviewDT)
 FROM Reviews as q WHERE q.CustomerName NOT NULL 
 ORDER BY q.CustomerName ASC, q.ReviewDT ASC;