18. Solutions: Comparing a Row to Previous Row

Comparing a Row to a Previous Row

SELECT occurred_at,
       total_amt_usd,
       LEAD(total_amt_usd) OVER (ORDER BY occurred_at) AS lead,
       LEAD(total_amt_usd) OVER (ORDER BY occurred_at) - total_amt_usd AS lead_difference
FROM (
SELECT occurred_at,
       SUM(total_amt_usd) AS total_amt_usd
  FROM orders 
 GROUP BY 1
) sub