update table using cursor? - sql

Question

Update
the purpose of this excerise is to eliminate passing the #RegModifiedDateTime again what i want is i should be able to read ModifiedDateTime by passing Id
example: if i pass Id = 564 then i should be able to read
`schoold_Id and ModifiedDateTime`
end update
here is how my table looks like for SchoolRegistration:
school_id id active modifydatetime
--------------------------------------------------
432 564 1 2008-12-14 13:15:38.750
342 564 1 2008-12-14 14:15:50.470
353 564 1 2008-12-14 14:19:46.703
end update
how do i loop to update my SchoolRegistration table? the id might have 1 or many rows in the SchoolRegistration but the thing is that RegModifiedDateTime is a unique for concurrency purpose and i should loop to get the right modifydatetime for that id.
alter procedure [dbo].[del_schoolRegistration]
#Id bigint,
#RegModifiedDateTime datetime
as
begin
declare #rowsAffected int
begin tran
--registration
update SchoolRegistration
set Active = 0,
ModifiedDateTime = getdate()
where (Id = #Id and RegModifiedDateTime = #RegModifiedDateTime or #RegModifiedDateTime is null )
if (#rowsAffected < 1) begin
rollback tran
end
else begin
commit tran
end
return #rowsAffected
end

Answer 1

--registration
;with tmp as (
select *, rn=ROW_NUMBER() over (partition by ID order by RegModifiedDateTime desc)
from SchoolRegistration
where (Id = #Id and RegModifiedDateTime = #RegModifiedDateTime or #RegModifiedDateTime is null ))
update tmp
set Active = 0,
ModifiedDateTime = getdate()
WHERE rn=1
What happens here is that if you did not know the RegModifiedDateTime you are looking for (by passing #RegModifiedDateTime as NULL), the query will catch them all for the ID due to #RegModifiedDateTime is null, but update ONLY the LATEST RegModifiedDateTime based on the row_numbering and CTE table definition.
EDIT
The above query retains the option to pass in a direct #RegModifiedDateTime should a record other than the latest need updating. To always update only the latest, drop the WHERE filter against #RegModifiedDateTime completely
--registration
;with tmp as (
select *, rn=ROW_NUMBER() over (partition by ID order by RegModifiedDateTime desc)
from SchoolRegistration
where Id = #Id)
update tmp
set Active = 0,
ModifiedDateTime = getdate()
WHERE rn=1

Answer 2

i endup using curor:
USE AdventureWorks
GO
DECLARE #ProductID INT
DECLARE #getProductID CURSOR
SET #getProductID = CURSOR FOR
SELECT ProductID
FROM Production.Product
OPEN #getProductID
FETCH NEXT
FROM #getProductID INTO #ProductID
WHILE ##FETCH_STATUS = 0
BEGIN
PRINT #ProductID
FETCH NEXT
FROM #getProductID INTO #ProductID
END
CLOSE #getProductID
DEALLOCATE #getProductID
GO