Question

This situation seems like it should be a simple task but I can’t come up with the solution. Imagine eight columns, four of which are bit columns (on/off) and the other four are reading values.

I want to create a view from this table, with another column for the range of the four reading values, based on those where their corresponding sensor alarm <> 1..

For examples purposes, we can use the following values.

Column1 – 12.44
Column1Alarm – 0

Column2 – 99.43
Column2Alarm – 0

Column3 – 4.43
Column3Alarm – 1

Column4 – 43.33
Column4Alarm – 0

For this example, the only values included in the range should be those coming from Column1, 2, and 4.

Thanks,
Tom

Answer 1

Editted as per @HLGM comments to make it a bit more robust.

Note that in it’s current form, I assume that when

• all alarms equal 1, the range should be NULL
• only one alarm equals 0, the range is the value of this alarm.

If this does not suffice, OP might clarify what should be returned instead.

SQL Statement

    ;WITH Alarm (C1, C1Alarm, C2, C2Alarm, C3, C3Alarm, C4, C4Alarm) AS (
        SELECT  12.44, 0, 99.43, 0, 4.43, 1, 43.33, 0
        UNION ALL SELECT 12.44, 1, 99.43, 0, 4.43, 1, 43.33, 0
        UNION ALL SELECT 1, 0, 2, 1, 3, 1, 4, 1
        UNION ALL SELECT 1, 1, 2, 1, 3, 1, 4, 1
    )
    , AddRowNumbers AS (
        SELECT  rowNumber = ROW_NUMBER() OVER (ORDER BY C1)
                , C1, C1Alarm
                , C2, C2Alarm
                , C3, C3Alarm
                , C4, C4Alarm
        FROM    Alarm   
    )
    , UnPivotColumns AS (
        SELECT  rowNumber, value = C1 FROM AddRowNumbers WHERE C1Alarm = 0
        UNION ALL SELECT rowNumber, C2 FROM AddRowNumbers WHERE C2Alarm = 0
        UNION ALL SELECT rowNumber, C3 FROM AddRowNumbers WHERE C3Alarm = 0
        UNION ALL SELECT rowNumber, C4 FROM AddRowNumbers WHERE C4Alarm = 0
    )
    SELECT  C1, C1Alarm
            , C2, C2Alarm
            , C3, C3Alarm
            , C4, C4Alarm
            , COALESCE(range1.range, range2.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  

Test script

;WITH Alarm (C1, C1Alarm, C2, C2Alarm, C3, C3Alarm, C4, C4Alarm) AS (
    SELECT  12.44, 0, 99.43, 0, 4.43, 1, 43.33, 0
    UNION ALL SELECT 12.44, 1, 99.43, 0, 4.43, 1, 43.33, 0
    UNION ALL SELECT 1, 0, 2, 1, 3, 1, 4, 1
    UNION ALL SELECT 1, 1, 2, 1, 3, 1, 4, 1
)
, AddRowNumbers AS (
    SELECT  rowNumber = ROW_NUMBER() OVER (ORDER BY C1)
            , C1, C1Alarm
            , C2, C2Alarm
            , C3, C3Alarm
            , C4, C4Alarm
    FROM    Alarm   
)
, UnPivotColumns AS (
    SELECT  rowNumber, value = C1 FROM AddRowNumbers WHERE C1Alarm = 0
    UNION ALL SELECT rowNumber, C2 FROM AddRowNumbers WHERE C2Alarm = 0
    UNION ALL SELECT rowNumber, C3 FROM AddRowNumbers WHERE C3Alarm = 0
    UNION ALL SELECT rowNumber, C4 FROM AddRowNumbers WHERE C4Alarm = 0
)
SELECT  C1, C1Alarm
        , C2, C2Alarm
        , C3, C3Alarm
        , C4, C4Alarm
        , COALESCE(range1.range, range2.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