Create a SQLite view where a row depends on the previous row

Question

I\'d like to create a view in SQLite where a field in one row depends on the value of a field in the previous row. I could do this in Oracle using the LAG analy

Answer 1

This should do the trick for every item (tested on SQLite):

SELECT 
    day
    ,price
    ,price - (SELECT t2.price 
              FROM mytable t2 
              WHERE 
                  t2.item = t1.item AND 
                  t2.day < t1.day      
              ORDER BY t2.day DESC
              LIMIT 1
             ) AS change
FROM mytable t1

This assumes the combination between day and item is unique. And the way it works is by taking all the values less than the given day, sorting descending and then LIMIT just the first value, simulating a LAG function.

For a LEAD behavior, just flip < to > and DESC to ASC.