Question

I am looking for a SQL Server function that I can supply 3 primary keys to ex.

functionFoo (@maxID, @minID, @testID) 

with the result being 1 (true) if the @testID version is between the @maxID and @minID version values where there are multiple columns with integers that are being compared.

I would also like the function to be able to handle open ended comparison, such that if the @maxID is NULL then it will just check if the @testID columns are greater than the @minID columns. Or if the @minID is NULL then it will check if the @testID columns are less than the @maxID columns.

Take this contrived example of comparing versions for software. Say you have multiple versioned software. For example say I have software1 with a version 1.6.6.978.73 and I now want a SQL Server function to determine if it falls between version 1.5.9.7 and version 1.6.7. My tables would be set up like below

Software Table

ID Version1 Version2 Version3 Version4 Version5
1  1        6        6        978      73
2  1        5        9        7        NULL
3  1        6        7        NULL     NULL

Where Version1 column is always weighted higher than the Version2 column (e.g. version 2.0 is higher than 1.99999). I’ve tried to go through each column and do a comparison and if the result is ambiguous then I move to the next column and again perform a comparison, but it seems tedious and difficult to read. Is there is a better/simpler way? Am I missing a built in SQL Server function? It is very similar to sorting something by alphabetical order, with a recursive nature where if the first comparison does not yield a determinate result we go one level deeper.

Answer 1

My approach to this problem was to select the 3 records, and sort them using the ORDER BY clause. Then apply a ROW_NUMBER() to the records and have some simple if statements determine the output of the function. This function only makes sure the @testID is betweeen the @minID and @maxID, thus @maxID could be less then @minID and it shouldn’t make a difference. That was fine for what I needed. I’m not sure it is the best way to do it, but I think it is very readable and the logic makes sense.

CREATE FUNCTION dbo.fnCompareSoftware
--Provide the function with the minID and maxID and the testID and it will determine if the testID is between the minID and maxID
(
 @minID int,
 @maxID int,
 @testID int
)
RETURNS bit
AS
BEGIN
DECLARE @rowTestNumber int
--inclusiveness
if @minID = @testID
  BEGIN
  RETURN 1
  END
if @maxID = @testID
  BEGIN
  RETURN 1
  END

SELECT @rowTestNumber = rowNumber FROM (
  --SELECT the 3 softwareID, then order them properly, then give them row numbers. Based on the results we can determine the result.
  SELECT
  ROW_NUMBER() OVER (ORDER BY Version1,Version2,Version3,Version4,Version5 ASC) AS rowNumber, Software.ID,Text
  FROM Software
  WHERE ID IN(@minID,@maxID,@testID)
) as Results
WHERE ID = @testID

--If minID is 0, then we are checking if the @testID is less than the @maxID. If so, @maxID will have the number 2 spot, and @testID will be #1
if @minID = 0 AND @maxID !=0 AND @rowTestNumber = 1
  BEGIN
  RETURN 1
  END
--If maxID is 0, then we are checking if the @testID is more than the @minID. If so, @minID will have the number 1 spot, and @testID will be #2
if @minID != 0 AND @maxID =0 AND @rowTestNumber = 2
  BEGIN
  RETURN 1
  END
if @minID != 0 AND @maxID !=0 AND @rowTestNumber = 2
  BEGIN
  RETURN 1
  END
--else we return 0  
RETURN 0
END
GO
;