Nested T-SQL Cursors Not Executing Correctly - tsql

Question

Before I get any militant cursor-bashing, let me say that I'm trying to use nested cursors to do something I only need to do once, but if I ran the operative stored procedure once for each user and agency I have to do it a few hundred times.
I thought a nested cursor in this case would save me some work, however, when I run this script it goes through the outer cursor only once, while the inner works just fine for that run. In the test case, the outer cursor set consists of two rows, and the inner one has about fifty. It goes through the first row of the outer cursor, and all fifty of the inner, but then it's done.
As you can see, I am saving off the result of the outer fetch (the '##fetch_status') so it doesn't interfere with the inner cursor.
I can't see what the problem is (obviously). Can anyone see what I can't?
declare #fetch_user int
declare #fetch_agency int
declare user_cursor cursor for
select upn from #users
open user_cursor
fetch next from user_cursor into #upn
select #fetch_user = ##fetch_status
while #fetch_user = 0
begin
declare agency_cursor cursor for
select agency, subagency from agency_system where system_id = 1
open agency_cursor
fetch next from agency_cursor into #agency, #subagency
select #fetch_agency = ##fetch_status
while #fetch_agency = 0
begin
select #upn, #agency, #subagency
EXEC AddUserToAgencyInRole
#upn
, #agency
, #subagency
, #system_id
, #role_id
, #response output
fetch next from agency_cursor into #agency, #subagency
select #fetch_agency = ##fetch_status
end
close agency_cursor
deallocate agency_cursor
fetch next from user_cursor into #upn
select #fetch_user = ##fetch_status
end
close user_cursor
deallocate user_cursor

Answer 1

The code looks like it should work. Throw in a count at the start:
select count(*) from #users
to double check the number of rows in #users ?

Answer 2

I'm not sure about troubleshooting the nested cursor other than that there is a way to get rid of it and have only one cursor.
Make this select statement using a cross-join:
SELECT u.upn, a.agency, a.subagency
FROM #users u, agency_system a
WHERE a.system_id = 1
Use that as your cursor definition. It should have every combination of user and agency/subagency.

Answer 3

I agree with Andomar it should work. This test case goes through the outer loop 4 times and the inner loop twice per iteration. (Which matches the number of rows in the respective tables)
set nocount on
DECLARE #upn INT, #agency INT, #subagency INT
CREATE TABLE #users (upn INT)
insert into #users select 1 union select 2 UNION select 3 UNION select 4
CREATE TABLE #agency_system(
agency INT,
subagency INT,
system_id INT)
insert into #agency_system
select 1,1,1 UNION select 2,2,1
declare #fetch_user int
declare #fetch_agency int
declare user_cursor cursor for
select upn from #users
open user_cursor
fetch next from user_cursor into #upn
select #fetch_user = ##fetch_status
while #fetch_user = 0
begin
PRINT 'In Outer While Loop'
declare agency_cursor cursor for
select agency, subagency from #agency_system where system_id = 1
open agency_cursor
fetch next from agency_cursor into #agency, #subagency
select #fetch_agency = ##fetch_status
while #fetch_agency = 0
begin
PRINT 'In Inner While Loop'
fetch next from agency_cursor into #agency, #subagency
select #fetch_agency = ##fetch_status
end
close agency_cursor
deallocate agency_cursor
fetch next from user_cursor into #upn
select #fetch_user = ##fetch_status
end
close user_cursor
deallocate user_cursor
drop TABLE #users
drop TABLE #agency_system

Answer 4

I appreciate all the responses.
I ended up eliminating the outer cursor and just manually running the inner one. This saved me from manually entering 393 separate entries. I just had to run the script three times.