Oracle grouped row counts to columns

First things first, I notice that your 'what I do now' query:

SELECT TOP (1)
    ca.SensorValue,
    ca.Date
FROM sys.partitions AS p
CROSS APPLY
(
    SELECT TOP (1)
        v.Date, 
        v.SensorValue
    FROM SensorValues AS v
    WHERE 
        $PARTITION.SensorValues_Date_PF(v.Date) = p.[partition_number]
        AND v.DeviceId = @fDeviceId
        AND v.SensorId = @fSensorId
        AND v.Date <= @fDate
    ORDER BY 
        v.Date DESC
) AS ca
WHERE 
    p.[partition_number] <= $PARTITION.SensorValues_Date_PF(@fDate)
    AND p.[object_id] = OBJECT_ID(N'dbo.SensorValues', N'U')
    AND p.index_id = 1
ORDER BY
    p.[partition_number] DESC, 
    ca.Date DESC;

...produces an execution plan like this:

This execution plan has an estimated total cost of 0.02 units. Over 50% of this estimated cost is the final Sort, running in Top-N mode. Now estimates are just that, but sorts can be expensive in general, so let's remove it without changing the semantics:

SELECT TOP (1)
    ca.SensorId,
    ca.SensorValue,
    ca.Date
FROM
(
    -- Partition numbers
    SELECT DISTINCT
        partition_number = prv.boundary_id
    FROM
        sys.partition_functions AS pf
    JOIN sys.partition_range_values AS prv ON
        prv.function_id = pf.function_id
    WHERE
        pf.name = N'SensorValues_Date_PF'
        AND prv.boundary_id <= $PARTITION.SensorValues_Date_PF(@fDate)
) AS p
CROSS APPLY
    (
    SELECT TOP (1)
        v.Date,
        v.SensorValue,
        v.SensorId
    FROM dbo.SensorValues AS v
    WHERE
        $PARTITION.SensorValues_Date_PF(v.Date) = p.partition_number
        AND v.DeviceId = @fDeviceId
        AND v.SensorId = @fSensorId
        AND v.Date <= @fDate
    ORDER BY
        v.Date DESC
  ) AS ca
ORDER BY
    p.partition_number DESC,
    ca.Date DESC

Now the execution plan has no blocking operators, and no sorts in particular. The estimated cost of the new query plan below is 0.01 units and the total cost is distributed evenly over the data access methods:

With the improvement in place, all we need to produce a result for each Sensor ID is to make a list of Sensor IDs and APPLY the previous code to each one:

SELECT
    PerSensor.SensorId,
    PerSensor.SensorValue,
    PerSensor.Date
FROM 
(
    -- Sensor ID list
    VALUES 
        (@fSensorId1),
        (@FSensorId2),
        (@FSensorId3)
) AS Sensor (Id)
CROSS APPLY
(
    -- Optimized code applied to each sensor
    SELECT TOP (1)
        ca.SensorId,
        ca.SensorValue,
        ca.Date
    FROM
    (
        -- Partition numbers
        SELECT DISTINCT
            partition_number = prv.boundary_id
        FROM
            sys.partition_functions AS pf
        JOIN sys.partition_range_values AS prv ON
            prv.function_id = pf.function_id
        WHERE
            pf.name = N'SensorValues_Date_PF'
            AND prv.boundary_id <= $PARTITION.SensorValues_Date_PF(@fDate)
    ) AS p
    CROSS APPLY
        (
        SELECT TOP (1)
            v.Date,
            v.SensorValue,
            v.SensorId
        FROM dbo.SensorValues AS v
        WHERE
            $PARTITION.SensorValues_Date_PF(v.Date) = p.partition_number
            AND v.DeviceId = @fDeviceId
            AND v.SensorId = Sensor.Id--@fSensorId1
            AND v.Date <= @fDate
        ORDER BY
            v.Date DESC
      ) AS ca
    ORDER BY
        p.partition_number DESC,
        ca.Date DESC
) AS PerSensor;

The query plan is:

Estimated query plan cost for three Sensor IDs is 0.011 - half that of the original single-sensor plan.

Thank you for SQLfiddle and sample data! I wish more questions started this way.

If you want all members regardless of whether they have an entry for that date, you want a LEFT OUTER JOIN. You were very close with this version however a little trick with outer joins is that if you add a filter to the outer table in the WHERE clause, you turn an outer join to an inner join, because it will exclude any rows that are NULL on that side (because it doesn't know if NULL would match the filter or not).

I modified the first query to get a row for every member:

SELECT Members.Member_ID
      ,Time_Entry.Date_Start
      ,Time_Entry.Hours_Actual
      ,Time_Entry.Hours_Bill
FROM dbo.Members
  LEFT OUTER JOIN dbo.Time_Entry
--^^^^ changed from FULL to LEFT
  ON Members.Member_ID = Time_Entry.Member_ID
  AND Time_Entry.Date_Start = '20131110';
--^^^ changed from WHERE to AND

I'll leave it as an exercise for the reader to take it from there and add the other columns, formatting, COALESCE etc.

Some other notes:

• please always use the schema prefix when creating and referencing objects

• please always use a length when converting to varchar etc.

• stay away from ambiguous, regional date formats like mm-dd-yyyy

• consider using aliases to make your queries easier to read. E.g. the above could be re-written as:

  SELECT m.Member_ID
    ,t.Date_Start
    ,t.Hours_Actual
    ,t.Hours_Bill
  FROM dbo.Members AS m
  LEFT OUTER JOIN dbo.Time_Entry AS t
  ON m.Member_ID = t.Member_ID
  AND t.Date_Start = '20131110';
  

  ... a lot tidier, IMHO, as long as you use sensible aliases.