从查询中删除重复项

Question

我在下面的查询中获取设备全天运行的百分比时间，但是由于数据中存在重复项，因此我无法轻易摆脱，这是最好的方法？

我试过使用distinct和Max（dtReading）

    SELECT DISTINCT
  workStationNo,
  controllerID,

  CAST(DATEPART(DAY, DATEADD(DAY, DATEDIFF(DAY, 0, MAX(dtReading)), 0)) AS varchar) AS date,
  (CAST(COUNT(*) AS float(1)) / CAST((DATEPART(HOUR, GETDATE()) * 30) AS float(1)) * CAST(100 AS float(1))) AS dayPercentage

FROM Controller
INNER JOIN ManufacturingLayout
  ON Controller.machID = ManufacturingLayout.workStationID
INNER JOIN ReaderData
  ON Controller.ctrlID = ReaderData.controllerID

WHERE dtReading >= CONVERT(datetime, '09/05/2018', 103)
AND dtReading <= DATEADD(HOUR, 24, CONVERT(datetime, '16/05/2018 23:59:59', 103))
AND (EventType = '(0x05)Open switch')
GROUP BY controllerID,
         DATEADD(DAY, DATEDIFF(DAY, 0, dtReading), 0),
         workStationNo
ORDER BY 1, 2

查询输出

Workstation no controllerID  date dayPercentage
ZW01006            38         15    80.20833
ZW01006            38         16    142.0833
ZW01007            30         15    62.5
ZW01007            30         16    120.2083
ZW01008            31         15    92.70833
ZW01008            31         16    141.0417
ZW01010            40         15    0.625

源数据

workStationNo   controllerID    dtReading
ZW01007            30           2018-05-16 15:42:39.000
ZW01007            30           2018-05-16 15:42:38.000
ZW01007            30           2018-05-16 15:40:38.000    <- duplicate
ZW01007            30           2018-05-16 15:40:38.000    <- duplicate 
ZW01007            30           2018-05-16 15:38:37.000
ZW01007            30           2018-05-16 15:38:37.000
ZW01007            30           2018-05-16 15:36:37.000
ZW01007            30           2018-05-16 15:36:37.000
ZW01007            30           2018-05-16 15:34:36.000

Answer 1

您可以将派生表用于JOIN到ReaderData ，以便在JOIN之前删除重复项：

...
INNER JOIN (SELECT DISTINCT controllerID, dtReading
            FROM ReaderData) ReaderData
...