MySQL-无效的按条款分组

Question

我有两个桌子。现在我有了这个查询：

SELECT
    p.date,
    HOUR(start) as startHour,
    (p.material * MIN(r.performance)) as energy
FROM
    PLANNING p
JOIN
    PERFORMANCE r ON p.`objectId` = r.`objectId` AND p.`mold` = r.`mold`
WHERE
    p.date = '2018-12-05'
GROUP BY
    startHour, p.material
ORDER BY
    startHour

显然，此查询使我每小时返回多行，因为我有多个objectId和模具对。确实，我每小时需要消耗一排能量，所以我已经尝试过这种方式：

SELECT
    p.date,
    HOUR(start) as startHour,
    SUM(p.material * MIN(r.performance)) as energy
FROM
    PLANNING p
JOIN
    PERFORMANCE r on p.`objectId` = r.`objectId` and p.`mold` = r.`mold`
WHERE
    p.date = '2018-12-05'
GROUP BY
    startHour
ORDER BY
    startHour

但是我得到Invalid use of group function