Question

I am partly on my way to solving this, but have hit a stumbling block, which I think can be solved with pivot(s).

I have the following SQL query, combining two temporary table variables (may change these to temporary tables, as I think performance maybe come a problem as they will be hit a large number of times):

SELECT MeterId, MeterDataOutput.BuildingId, MeterDataOutput.Value, 
            MeterDataOutput.TimeStamp, UtilityId, SnapshotId 
        FROM @MeterDataOutput as MeterDataOutput INNER JOIN @InsertOutput AS InsertOutput 
                ON MeterDataOutput.BuildingId = InsertOutput.BuildingId
                AND MeterDataOutput.[Timestamp] = InsertOutput.[TimeStamp]

This produces the following table:

I have then modified the query to group by BuildingId, SnapshotId, Timestamp, Utility and applied the SUM() function to aggregate the Value field (and dropped the MeterId as its not required), as follows:

SELECT MeterDataOutput.BuildingId, SUM(MeterDataOutput.Value) AS Value, MeterDataOutput.TimeStamp, UtilityId, SnapshotId 
FROM @MeterDataOutput as MeterDataOutput 
INNER JOIN @InsertOutput AS InsertOutput 
    ON MeterDataOutput.BuildingId = InsertOutput.BuildingId
    AND MeterDataOutput.[Timestamp] = InsertOutput.[TimeStamp]
GROUP BY MeterDataOutput.BuildingId, MeterDataOutput.TimeStamp, UtilityId, SnapshotId

This query the provides me with the following table:

Now the bit I’m having trouble with is transforming the UtilityId values to columns, and placing the values from the Value field under each column. I.e:

For reference buildingId, Timestamp, Snapshot and Value are variable. UtilityId value 6 is always ‘Electricity’, 7 is always ‘Gas’ and 8 is always ‘Water’.

I’m actually starting to get the hand of the SQL lark 🙂

Answer 1

Maybe something like this:

SELECT
    pvt.BuildingId,
    pvt.SnapshotId,
    pvt.TimeStamp,
    pvt.[6] AS Electricity,
    pvt.[7] AS Gas,
    pvt.[8] AS Water
FROM
    (
    SELECT 
        MeterDataOutput.BuildingId, 
        MeterDataOutput.Value, 
        MeterDataOutput.TimeStamp, 
        UtilityId, 
        SnapshotId 
    FROM @MeterDataOutput as MeterDataOutput 
    INNER JOIN @InsertOutput AS InsertOutput 
        ON MeterDataOutput.BuildingId = InsertOutput.BuildingId
        AND MeterDataOutput.[Timestamp] = InsertOutput.[TimeStamp]
    ) AS SourceTable
PIVOT
(
    SUM(Value)
    FOR UtilityId IN ([6],[7],[8])
) AS pvt