在嘗試獲得每小時的電壓穩定性時，我遇到了組功能錯誤。如下圖所示的表格。 表格影像
SELECT ip,
SUM(CASE HOUR(time) WHEN '1' THEN CAST(AVG(IF(volt=0,0,1)) AS DECIMAL(2,1)) ELSE 0 END) AS '1',
SUM(CASE HOUR(time) WHEN '2' THEN CAST(AVG(IF(volt=0,0,1)) AS DECIMAL(2,1)) ELSE 0 END) AS '2',
SUM(CASE HOUR(time) WHEN '3' THEN CAST(AVG(IF(volt=0,0,1)) AS DECIMAL(2,1)) ELSE 0 END) AS '3'
FROM UPS_Status
WHERE time BETWEEN NOW() - INTERVAL 24 hour AND NOW()
GROUP BY ip, HOUR(time)
uj5u.com熱心網友回復：
HOUR(time)不屬于GROUP BY從句。嘗試洗掉它：
SELECT
ip,
SUM(CASE HOUR(time) WHEN 1 THEN CAST(IF(volt=0, 0, 1) AS DECIMAL(2,1)) ELSE 0 END) AS `1`,
SUM(CASE HOUR(time) WHEN 2 THEN CAST(IF(volt=0, 0, 1) AS DECIMAL(2,1)) ELSE 0 END) AS `2`,
SUM(CASE HOUR(time) WHEN 3 THEN CAST(IF(volt=0, 0, 1) AS DECIMAL(2,1)) ELSE 0 END) AS `3`
FROM UPS_Status
WHERE
time BETWEEN NOW() - INTERVAL 24 hour AND NOW()
GROUP BY ip;
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