Snelheid door eenvoud

-- keep it simple - make it fast

SELECT
    o.id,
    o.order_date,
    c.name,
    SUM(oi.amount) AS total

FROM orders o

JOIN customers c
    ON c.id = o.customer_id

JOIN order_items oi
    ON oi.order_id = o.id

WHERE o.status = 'completed'

GROUP BY
    o.id,
    c.name,
    o.order_date

ORDER BY total DESC;

-- data. logic. impact.