我有两张table。现在我有一个问题：

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，这个查询每小时返回多行，因为我有多个objectid和mold对。事实上，我需要每小时有一排能量总和，所以我试着这样做：

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

但我明白了 Invalid use of group function