加快SQL查詢

Question

我有正在採取一些嚴重的時間上比任何過去，說，小時值數據的較舊的執行查詢。這將創建一個將用於數據挖掘的視圖，所以期望它能夠搜索數週或數月的數據並在合理的時間內返回（即使幾分鐘也沒問題）...我運行的日期範圍爲10/3/2011 12:00pm至10/3/2011 1:00pm，花了44分鐘！）

問題在於底部有兩個LEFT OUTER JOIN s。當我把它們拿出來時，它可以在大約10秒內運行。但是，這些是這個查詢的麪包和黃油。

這一切都是從一個表來。該查詢返回的結果與原始表格不同的是xweb_range。 xweb_range是計算字段列（範圍），其中其對應的[LO,LC,RO,RC]_Sensor_Alarm = 0這隻會從[LO,LC,RO,RC]_Avg使用的值（不要範圍計算包括如果傳感器報警= 1）

WITH Alarm (sub_id, 
LO_Avg, LO_Sensor_Alarm, LC_Avg, LC_Sensor_Alarm, RO_Avg, RO_Sensor_Alarm, RC_Avg, RC_Sensor_Alarm) AS (
SELECT sub_id, LO_Avg, LO_Sensor_Alarm, LC_Avg, LC_Sensor_Alarm, RO_Avg, RO_Sensor_Alarm, RC_Avg, RC_Sensor_Alarm 
FROM dbo.some_table 
where sub_id <> '0' 
) 
, AddRowNumbers AS (
SELECT rowNumber = ROW_NUMBER() OVER (ORDER BY LO_Avg) 
    , sub_id 
    , LO_Avg, LO_Sensor_Alarm 
    , LC_Avg, LC_Sensor_Alarm 
    , RO_Avg, RO_Sensor_Alarm 
    , RC_Avg, RC_Sensor_Alarm 
FROM Alarm 
) 
, UnPivotColumns AS (
SELECT rowNumber, value = LO_Avg FROM AddRowNumbers WHERE LO_Sensor_Alarm = 0 
UNION ALL SELECT rowNumber, LC_Avg FROM AddRowNumbers WHERE LC_Sensor_Alarm = 0 
UNION ALL SELECT rowNumber, RO_Avg FROM AddRowNumbers WHERE RO_Sensor_Alarm = 0 
UNION ALL SELECT rowNumber, RC_Avg FROM AddRowNumbers WHERE RC_Sensor_Alarm = 0 
) 
SELECT rowNumber.sub_id 
    , cds.equipment_id 
    , cds.read_time 
    , cds.LC_Avg 
    , cds.LC_Dev 
    , cds.LC_Ref_Gap 
    , cds.LC_Sensor_Alarm 
    , cds.LO_Avg 
    , cds.LO_Dev 
    , cds.LO_Ref_Gap 
    , cds.LO_Sensor_Alarm 
    , cds.RC_Avg 
    , cds.RC_Dev 
    , cds.RC_Ref_Gap 
    , cds.RC_Sensor_Alarm 
    , cds.RO_Avg 
    , cds.RO_Dev 
    , cds.RO_Ref_Gap 
    , cds.RO_Sensor_Alarm 
    , COALESCE(range1.range, range2.range) AS xweb_range 
FROM AddRowNumbers rowNumber 
    LEFT OUTER JOIN (SELECT rowNumber, range = MAX(value) - MIN(value) FROM UnPivotColumns GROUP BY rowNumber HAVING COUNT(*) > 1) range1 ON range1.rowNumber = rowNumber.rowNumber 
    LEFT OUTER JOIN (SELECT rowNumber, range = AVG(value) FROM UnPivotColumns  GROUP BY rowNumber HAVING COUNT(*) = 1) range2 ON range2.rowNumber = rowNumber.rowNumber 
    INNER JOIN dbo.some_table cds 
    ON rowNumber.sub_id = cds.sub_id 

Answer 1

這是很難理解您的查詢到底是什麼試圖不知道域名。然而，在我看來，像你的查詢只是試圖找到，在dbo.some_table每一行，其中sub_id不爲0，下面列的記錄範圍內（或者，如果只有一個匹配，即單值）：

• LO_AVG當LO_SENSOR_ALARM = 0
• LC_AVG當LC_SENSOR_ALARM = 0
• RO_AVG噹噹RC_SENSOR_ALARM = 0

您構造的本曲RO_SENSOR_ALARM = 0

RC_AVG爲每行分配一個連續的行號，將_AVG列及其行號未賦值，按行號計算範圍聚合分組，然後按行號連接回原始記錄。 CTE沒有實現結果（也沒有按照評論中的討論進行索引）。所以每個參考AddRowNumbers是昂貴的，因爲ROW_NUMBER() OVER (ORDER BY LO_Avg)是一種。

而不是削減該表最多隻是行號加入它重新走到一起的，爲什麼不這樣做：

SELECT cds.sub_id 
    , cds.equipment_id 
    , cds.read_time 
    , cds.LC_Avg 
    , cds.LC_Dev 
    , cds.LC_Ref_Gap 
    , cds.LC_Sensor_Alarm 
    , cds.LO_Avg 
    , cds.LO_Dev 
    , cds.LO_Ref_Gap 
    , cds.LO_Sensor_Alarm 
    , cds.RC_Avg 
    , cds.RC_Dev 
    , cds.RC_Ref_Gap 
    , cds.RC_Sensor_Alarm 
    , cds.RO_Avg 
    , cds.RO_Dev 
    , cds.RO_Ref_Gap 
    , cds.RO_Sensor_Alarm 

    --if the COUNT is 0, xweb_range will be null (since MAX will be null), if it's 1, then use MAX, else use MAX - MIN (as per your example) 
    , (CASE WHEN stats.[Count] < 2 THEN stats.[MAX] ELSE stats.[MAX] - stats.[MIN] END) xweb_range 

FROM dbo.some_table cds 

    --cross join on the following table derived from values in cds - it will always contain 1 record per row of cds 
    CROSS APPLY 
    (
     SELECT COUNT(*), MIN(Value), MAX(Value) 
     FROM 
     (
      --construct a table using the column values from cds we wish to aggregate 
      VALUES (LO_AVG, LO_SENSOR_ALARM), 
        (LC_AVG, LC_SENSOR_ALARM), 
        (RO_AVG, RO_SENSORALARM), 
        (RC_AVG, RC_SENSOR_ALARM) 


     ) x (Value, Sensor_Alarm) --give a name to the columns for _AVG and _ALARM 
     WHERE Sensor_Alarm = 0 --filter our constructed table where _ALARM=0 

    ) stats([Count], [Min], [Max]) --give our derived table and its columns some names 

WHERE cds.sub_id <> '0' --this is a filter carried over from the first CTE in your example