SQL Server - How Do I Create Increments in a Query - sql-server-2008-r2

Question

First off, I'm using SQL Server 2008 R2
I am moving data from one source to another. In this particular case there is a field called SiteID. In the source it's not a required field, but in the destination it is. So it was my thought, when the SiteID from the source is NULL, to sort of create a SiteID "on the fly" during the query of the source data. Something like a combination of the state plus the first 8 characters of a description field plus a ten digit number incremented.
At first I thought it might be easy to use a combination of date/time + nanoseconds but it turns out that several records can be retrieved within a nanosecond leading to duplicate SiteIDs.
My second idea was to create a table that contained an identity field plus a function that would add a record to increment the identity field and then return it (the function would also delete all records where the identity field is less than the latest saving space). Unfortunately after I got it written, when trying to "CREATE" the function I got a notice that INSERTs are not allowed in functions.
I could (and did) convert it to a stored procedure, but stored procedures are not allowed in select queries.
So now I'm stuck.
Is there any way to accomplish what I'm trying to do?

Answer 1

This script may take time to execute depending on the data present in the table, so first execute on a small sample dataset.
DECLARE #TotalMissingSiteID INT = 0,
#Counter INT = 0,
#NewID BIGINT;
DECLARE #NewSiteIDs TABLE
(
SiteID BIGINT-- Check the datatype
);
SELECT #TotalMissingSiteID = COUNT(*)
FROM SourceTable
WHERE SiteID IS NULL;
WHILE(#Counter < #TotalMissingSiteID )
BEGIN
WHILE(1 = 1)
BEGIN
SELECT #NewID = RAND()* 1000000000000000;-- Add your formula to generate new SiteIDs here
-- To check if the generated SiteID is already present in the table
IF ( ISNULL(( SELECT 1
FROM SourceTable
WHERE SiteID = #NewID),0) = 0 )
BREAK;
END
INSERT INTO #NewSiteIDs (SiteID)
VALUES (#NewID);
SET #Counter = #Counter + 1;
END
INSERT INTO DestinationTable (SiteID)-- Add the extra columns here
SELECT ISNULL(MainTable.SiteID,NewIDs.SiteID) SiteID
FROM (
SELECT SiteID,-- Add the extra columns here
ROW_NUMBER() OVER(PARTITION BY SiteID
ORDER BY SiteID) SerialNumber
FROM SourceTable
) MainTable
LEFT JOIN ( SELECT SiteID,
ROW_NUMBER() OVER(ORDER BY SiteID) SerialNumber
FROM #NewSiteIDs
) NewIDs
ON MainTable.SiteID IS NULL
AND MainTable.SerialNumber = NewIDs.SerialNumber