Oracle Database SQL 12c 1z0-071 Exam Practice Test 4

Explanation/Reference:
Explanation:
Sample
SELECT tr_sub.cur_tt, tr_sub.item, sum(tr.quantity), sum(tr.quantity*tr.unit_price)
FROM
(SELECT tr1.transaction_time as cur_tt, max(tr2.transaction_time) as prev_tt, tr1.item as item,
IF (tr1.unit_price=tr2.unit_price, tr1.unit_price, tr2.unit_price) as t_p
FROM transactions tr1 LEFT JOIN transactions tr2 ON
tr1.transaction_time>=tr2.transaction_time AND tr1.item=tr2.item
GROUP BY tr1.item, tr1.transaction_time, t_p
Reference: https://stackoverflow.com/questions/50771172/sql-query-get-total-value-based-on-different-unit-price-quantity-at-different-ti