Sum Up An Unknown Number Of Records

With this algorithm you can sum up an unkown number of records, so that an aggregation matches a fixed value.
If there is not an exakt match available, the algorithm returns the nearest possible value!-- Initialize the search parameter
DECLARE@WantedValue INT

SET@WantedValue = 349

-- Stage the source data
DECLARE@Data TABLE
(
RecID INT IDENTITY(1, 1) PRIMARY KEY CLUSTERED,
MaxItems INT,
CurrentItems INT DEFAULT 0,
FaceValue INT,
BestUnder INT DEFAULT 0,
BestOver INT DEFAULT 1
)

-- Aggregate the source data
INSERT@Data
(
MaxItems,
FaceValue
)
SELECTCOUNT(*),
Qty
FROM(
SELECT 899 AS Qty UNION ALL
SELECT 100 UNION ALL
SELECT 95 UNION ALL
SELECT 50 UNION ALL
SELECT 55 UNION ALL
SELECT 40 UNION ALL
SELECT 5 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 50 UNION ALL
SELECT 250 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 90 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 50 UNION ALL
SELECT 350 UNION ALL
SELECT 450 UNION ALL
SELECT 450 UNION ALL
SELECT 100 UNION ALL
SELECT 100 UNION ALL
SELECT 50 UNION ALL
SELECT 50 UNION ALL
SELECT 50 UNION ALL
SELECT 1 UNION ALL
SELECT 10 UNION ALL
SELECT 1
) AS d
GROUP BYQty
ORDER BYQty DESC

-- Declare some control variables
DECLARE@CurrentSum INT,
@BestUnder INT,
@BestOver INT,
@RecID INT

-- If productsum is less than or equal to the wanted sum, select all items!
IF (SELECT SUM(MaxItems * FaceValue) FROM @Data) <= @WantedValue
BEGIN
SELECTMaxItems AS Items,
FaceValue
FROM@Data

RETURN
END

-- Delete all unworkable FaceValues
DELETE
FROM@Data
WHEREFaceValue > (SELECT MIN(FaceValue) FROM @Data WHERE FaceValue >= @WantedValue)

-- Update MaxItems to a proper value
UPDATE@Data
SETMaxItems =CASE
WHEN 1 + (@WantedValue - 1) / FaceValue < MaxItems THEN 1 + (@WantedValue - 1) / FaceValue
ELSE MaxItems
END

-- Update BestOver to a proper value
UPDATE@Data
SETBestOver = MaxItems

-- Initialize the control mechanism
SELECT@RecID = MIN(RecID),
@BestUnder = 0,
@BestOver = SUM(BestOver * FaceValue)
FROM@Data

-- Do the loop!
WHILE @RecID IS NOT NULL
BEGIN
-- Reset all "bits" not incremented
UPDATE@Data
SETCurrentItems = 0
WHERERecID < @RecID

-- Increment the current "bit"
UPDATE@Data
SETCurrentItems = CurrentItems + 1
WHERERecID = @RecID

-- Get the current sum
SELECT@CurrentSum = SUM(CurrentItems * FaceValue)
FROM@Data
WHERECurrentItems > 0

-- Stop here if the current sum is equal to the sum we want
IF @CurrentSum = @WantedValue
BREAK
ELSE
-- Update the current BestUnder if previous BestUnder is less
IF @CurrentSum > @BestUnder AND @CurrentSum < @WantedValue
BEGIN
UPDATE@Data
SETBestUnder = CurrentItems

SET@BestUnder = @CurrentSum
END
ELSE
-- Update the current BestOver if previous BestOver is more
IF @CurrentSum > @WantedValue AND @CurrentSum < @BestOver
BEGIN
UPDATE@Data
SETBestOver = CurrentItems

SET@BestOver = @CurrentSum
END

-- Find the next proper "bit" to increment
SELECT@RecID = MIN(RecID)
FROM@Data
WHERECurrentItems < MaxItems
END

-- Now we have to investigate which type of sum to return
IF @RecID IS NULL
IF @WantedValue - @BestUnder < @BestOver - @WantedValue
-- If BestUnder is closer to the sum we want, choose that
SELECTBestUnder AS Items,
FaceValue
FROM@Data
WHEREBestUnder > 0
ELSE
-- If BestOver is closer to the sum we want, choose that
SELECTBestOver AS Items,
FaceValue
FROM@Data
WHEREBestOver > 0
ELSE
-- We have an exact match
SELECTCurrentItems AS Items,
FaceValue
FROM@Data
WHERECurrentItems > 0With references to
http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=73540
http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=73610
http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=78015
http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=79505


Peter Larsson
Helsingborg, Sweden