SELECT
pwl.product_id,
pwl.warehouse_id,
pwl.base_price,
pwl.stock_quantity,
(SELECT pwl2.stock_quantity FROM product_warehouse_logs pwl2 WHERE pwl2.product_id = pwl.product_id AND pwl2.warehouse_id = pwl.warehouse_id AND pwl2.logged_at < pwl.logged_at AND pwl2.stock_quantity != pwl.stock_quantity LIMIT 1) as previous_stock_quantity
FROM product_warehouse_logs pwl
WHERE pwl.logged_at > '2018-04-01'
ORDER BY previous_stock_quantity ASC