Mysql 以更好的方式编写此SQL查询的好方法是什么？

非常混乱，但我创建此查询是为了查找一组行的摘要。Min和max timestamp很简单，但是为了找到速度为零而不是零的行数，我做了一个丑陋的破解。我相信有更好的方法可以做到这一点

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更新：是什么？请参阅将由CodeIgniter的不成熟查询生成器替换。遗憾的是，它还不支持命名参数

应该包括DeviceID，这样才有意义。试试这个：

SELECT
    MAX(timestamp) as end,
    MIN(timestamp) as start, 
    (MAX(odometerKM) - MIN(odometerKM)) as distanceTravelled,
    ( SELECT COUNT(*) FROM EventData WHERE speedKPH = 0 AND timestamp >= ? AND timestamp <= ? AND  deviceID = ?)  as stopsDuration,
    ( SELECT COUNT(*) FROM EventData WHERE speedKPH != 0 AND timestamp >= ? AND timestamp <= ? AND  deviceID = ? )  as tripDuration,
    (MAX(odometerKM) - MIN(odometerKM)) / ( SELECT fuelEconomy FROM Device WHERE deviceID = ?) as fuelConsumption
FROM EventData
WHERE deviceID = ? AND timestamp >= ? AND timestamp <= ?

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我会去掉列子查询。您可以这样计算停止持续时间和tripDuration我暂时不考虑燃油消耗：

把所有这些放在一起，你会得到这样的结果，至少在纸上应该更快：

SELECT
  (MAX(odometerKM) - MIN(odometerKM)) / dv.fuelEconomy as fuelConsumption
FROM
  EventData,
  (SELECT Device.fuelEconomy FROM Device WHERE DeviceId = ?) dv
WHERE deviceID = ? AND timestamp >= ? AND timestamp <= ?

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难道您没有忘记包含deviceID=的条件吗？在你的前两个子查询中？@Yak:是的。让我编辑一下。另外，看起来相同的两个子查询实际上计算了事件数，而不是持续时间？为了进一步减少它，创建另一个带有WHERE条件的子查询表并完全消除WHERE不是更好吗？我考虑过这一点，但我不确定它是否会破坏start和/或end和/或distance值。我从来没有打算测试这个，所以我在做了100%确定的事情后就停止了。如果你能把它减少到这个程度，你一定要把它作为一个答案。请随意使用我的查询作为起点-我对此没有任何问题：

SELECT
  MAX(timestamp) as end, MIN(timestamp) as start, 
  MAX(odometerKM) - MIN(odometerKM) as distanceTravelled,
  COUNT(speedKPH = 0 AND timestamp >= ? AND timestamp <= ?) as stopsDuration
  COUNT(speedKPH != 0 AND timestamp >= ? AND timestamp <= ?) as tripDuration
FROM EventData WHERE deviceID = ? AND timestamp >= ? AND timestamp <= ?

SELECT
  (MAX(odometerKM) - MIN(odometerKM)) / dv.fuelEconomy as fuelConsumption
FROM
  EventData,
  (SELECT Device.fuelEconomy FROM Device WHERE DeviceId = ?) dv
WHERE deviceID = ? AND timestamp >= ? AND timestamp <= ?

SELECT
  MAX(timestamp) as end, MIN(timestamp) as start, 
  MAX(odometerKM) - MIN(odometerKM) as distanceTravelled,
  COUNT(speedKPH = 0 AND timestamp >= ? AND timestamp <= ?) as stopsDuration
  COUNT(speedKPH != 0 AND timestamp >= ? AND timestamp <= ?) as tripDuration,
  (MAX(odometerKM) - MIN(odometerKM)) / dv.fuelEconomy as fuelConsumption
FROM
  EventData,
  (SELECT Device.fuelEconomy FROM Device WHERE DeviceId = ?) dv
WHERE deviceID = ? AND timestamp >= ? AND timestamp <= ?