Question

我正在研究MySQL查询以返回一些特定结果。我很亲密。现在，我需要计算2列之间的TIMEDIFF。这是我目前的查询：

SELECT DATE_FORMAT(PunchDateTime, '%W') DAY, MAX(CASE WHEN PunchEvent = 'ClockIn' THEN DATE_FORMAT(PunchDateTime, '%r') END) AS 'Clock In', MAX(CASE WHEN PunchEvent = 'BreakOut' THEN 
    DATE_FORMAT(PunchDateTime, '%r') END) AS 'Break Out', MAX(CASE WHEN PunchEvent = 'BreakIn' THEN DATE_FORMAT(PunchDateTime, '%r') END) 'Break In', MAX(CASE WHEN PunchEvent = 'ClockOut' THEN 
    DATE_FORMAT(PunchDateTime, '%r') END) 'Clock Out', TIMEDIFF('Clock In', 'Break Out') AS Total FROM timeclock_punchlog WHERE EmpID = 456 GROUP BY 
    DATE_FORMAT(PunchDateTime, '%W') ORDER BY PunchDateTime;

现在，Total显示00:00:00。我有什么想法可以做到这一点？谢谢麦克

Answer 1

经过大量的谷歌搜索和修补，我想通了。我发现你不能在TIMEDIFF函数中使用先前在查询中创建的别名。我基本上不得不使用我用来创建别名的整个公式代替TIMEDIFF函数中的别名。这是我的疑问：

SELECT  DATE_FORMAT(PunchDateTime, '%W') DAY, MAX(CASE WHEN PunchEvent = 'ClockIn' THEN DATE_FORMAT(PunchDateTime, '%T') END) AS 'Clock In', MAX(CASE WHEN PunchEvent = 'BreakOut' THEN DATE_FORMAT(PunchDateTime, '%T') END) AS 'Break Out', MAX(CASE WHEN PunchEvent = 'BreakIn' THEN DATE_FORMAT(PunchDateTime, '%T') END) 'Break In', MAX(CASE WHEN PunchEvent = 'ClockOut' THEN DATE_FORMAT(PunchDateTime, '%T') END) 'Clock Out', (TIMEDIFF(MAX(CASE WHEN PunchEvent = 'clockout' THEN DATE_FORMAT(PunchDateTime, '%T') END), MAX(CASE WHEN PunchEvent = 'breakin' THEN DATE_FORMAT(PunchDateTime, '%T') END))) AS Total FROM timeclock_punchlog WHERE EmpID = 456 GROUP BY DATE_FORMAT(PunchDateTime, '%W') ORDER BY PunchDateTime;

我还必须将我的％r更改为％T，以便根据军事时间而不是标准的上午/下午时间正确计算TIMEDIFF。希望这有助于某人！麦克

从mysql中创建的列中提取timediff

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