Subquery in DECLARE statement brings back more than one value - sql-server

Question

I have the stored procedure below that I need help on. Its purpose is to find differences between a staging DB and the production DB. When it finds the difference, the stored procedure will update the production DB with the correct information. The problem is that sometimes there is more than one difference between the DBs. The stored procedure can only handle one difference between the DBs at a time. I want the stored procedure to be able to handle as many differences as it finds. If it can only handle one difference at a time, the stored procedure would need to be running continually. Any ideas or help is greatly appreciated.
`BEGIN TRANSACTION
DECLARE #FILENUM NVARCHAR(30)
SET #FILENUM = ( SELECT TOP 1 B.ID FROM DBO.ABC_FILE_NUMBER F WITH ( NOLOCK )
JOIN DBO.REL_PRIMARY_NUMBER R WITH ( NOLOCK ) ON F.ID = R.FILE_NUMBER_ID
JOIN DBO.ABC_PRIMARY_NUMBER P WITH ( NOLOCK ) ON R.PRIMARY_NUMBER_ID = P.ID
JOIN DBO.STAGINGDATA S WITH ( NOLOCK ) ON F.FILE_NUMBER_ALIAS = S.ID
WHERE S.PRIMARYNUMBER <> P.PRIMARY_NUMBER_ALIAS)
DECLARE #PRIMNUM NVARCHAR(30)
SET #PRIMNUM = ( SELECT DISTINCT P.ID FROM DBO.STAGINGDATA S WITH ( NOLOCK )
JOIN DBO.ABC_PRIMARY_NUMBER P WITH ( NOLOCK ) ON P.PRIMARY_NUMBER_ALIAS = S.PRIMARYNUMBER
WHERE S.ID = ( SELECT F.FILE_NUMBER_ALIAS FROM ABC_FILE_NUMBER WHERE ID = #FILENUM))
UPDATE DBO.REL_PRIMARY_NUMBER
SET PRIMARY_NUMBER_ID = #PRIMNUM
WHERE FILE_NUMBER_ID = #FILENUM
UPDATE DBO.ABC_WORKSPACE
SET PRIMARY_NUMBER_ID = #PRIMNUM
WHERE FILE_NUMBER_ID = #FILENUM
UPDATE DBO.ABC_DOCUMENT
SET PRIMARY_NUMBER_ID = #PRIMNUM
WHERE FILE_NUMBER_ID = #FILENUM
UPDATE DBO.ABC_FILE_NUMBER
SET MODIFIED_TIME = GETDATE(), MODIFIED_BY_ID = '21403'
WHERE FILE_NUMBER_ID = #FILENUM
COMMIT`

Answer 1

You can construct a loop as below to "walk" through each #FILENUM and do the work using the same scripts you are using now. A better option would be to rewrite each DML operation to perform the work in a set based way and act on all the rows at once, but that might not be an option for you depending on what other actions you are performing.
Here's a simple setup to loop through each FileNum:
declare #Process table (ProcessId int identity(1,1), FileNum nvarchar(30));
-- stage *all* the fileNums (perhaps in some order?)
insert into #Process (FileNum)
SELECT B.ID FROM DBO.ABC_FILE_NUMBER F WITH ( NOLOCK )
JOIN DBO.REL_PRIMARY_NUMBER R WITH ( NOLOCK ) ON F.ID = R.FILE_NUMBER_I
JOIN DBO.ABC_PRIMARY_NUMBER P WITH ( NOLOCK ) ON R.PRIMARY_NUMBER_ID = P.ID
JOIN DBO.STAGINGDATA S WITH ( NOLOCK ) ON F.FILE_NUMBER_ALIAS = S.ID
WHERE S.PRIMARYNUMBER <> P.PRIMARY_NUMBER_ALIAS
declare #ProcessId int,
#FileNum nvarchar(30);
select #ProcessId = min(ProcessId) from #Process;
while #ProcessId is not null
begin
select #FileNum = FileNum from #Process where ProcessId = #ProcessId;
print 'Working on FileNum: ' + #FileNum;
/*
do your work here
*/
select #ProcessId = min(ProcessId) from #Process where ProcessId > #ProcessId;
end
The set based operation would look something like:
declare #Stage table (FileNum nvarchar(30), PrimNum nvarchar(30) primary key (FileNum));
-- stage the (FileNum:PrimNum) dataset
insert into #Stage (FileNum)
select FileNum, PrimNum from dbo.yourTables where yourColumn ...
--now perform set based updates
UPDATE rpn
SET PRIMARY_NUMBER_ID = s.PRIMNUM
from #Stage s
join DBO.REL_PRIMARY_NUMBER rpn on
s.FileNum = rpn.FILE_NUMBER_ID
UPDATE aw
SET PRIMARY_NUMBER_ID = s.PRIMNUM
from #Stage s
join DBO.ABC_WORKSPACE aw on
s.FileNum = aw.FILE_NUMBER_ID
-- and so on...