first attempt at a sproc transaction - tsql

Question

I am trying to write a sproc with a transaction. Can anybody tell me if there would be any issues with code below, or if it will work as intended?
ALTER procedure [dbo].[DeleteMetricMeter]
(
#SectionID int,
#MetricMeterID int,
#Result bit output
)
as
declare #MetricMeterCount int
declare #err int
declare #rowcount int
set xact_abort on
begin tran
select #MetricMeterCount = count(*) from luMetricMeters
where fkSectionID = #SectionID
select #err = ##error, #rowcount = ##rowcount
if (#err <> 0) or (#rowcount = 0)
begin
goto on_error
end
delete from luMetricMeterList
where pkMetricMeterID = #MetricMeterID
select #err = ##error, #rowcount = ##rowcount
if (#err <> 0) or (#rowcount = 0)
begin
goto on_error
end
delete from luMetricMeters
where pkMetricMeterID = #MetricMeterID
select #err = ##error, #rowcount = ##rowcount
if (#err <> 0) or (#rowcount = 0)
begin
goto on_error
end
if (#MetricMeterCount = 1)
begin
delete from luMetricSections
where pkSectionID = #SectionID
select #err = ##error, #rowcount = ##rowcount
if (#err <> 0) or (#rowcount = 0)
begin
goto on_error
end
end
commit tran
set #result = 1
return #result
on_error:
rollback tran
set #result = 0
return #result

Answer 1

If you are using Sql Server 2005+, I would recomend rather using TRY...CATCH (Transact-SQL) and have a look at section [B. Using TRY…CATCH in a transaction]
This will GREATLY simplify your procedure.

Answer 2

There are a few issues with the procedure:
You should not evaluate rowcount unless it really indicates an error. When there is no data deleted there is no need to rollback.
Your code is not thread safe. The MetricMeterCount query should be changed to this to prevent other threads from performing the delete in between your select & the execution of the delete:
select #MetricMeterCount = count(*)
from luMetricMeters with (xlock, serializable)
where fkSectionID = #SectionID
I would write the code like this:
ALTER procedure [dbo].[DeleteMetricMeter]
(
#SectionID int,
#MetricMeterID int,
#Result bit output
)
as
DECLARE #MetricMeterCount int
DECLARE #err int
DECLARE #rowcount int
SET xact_abort ON
BEGIN TRAN
DELETE FROM luMetricMeterList
WHERE pkMetricMeterID = #MetricMeterID
SELECT #err = ##error
IF (#err <> 0)
GOTO on_error
DELETE FROM luMetricMeters
WHERE pkMetricMeterID = #MetricMeterID
SELECT #err = ##error
IF (#err <> 0)
GOTO on_error
IF EXISTS (SELECT *
FROM luMetricMeters WITH (xlock, serializable)
WHERE fkSectionID = #SectionID)
BEGIN
DELETE FROM luMetricSections
WHERE pkSectionID = #SectionID
SELECT #err = ##error
IF (#err <> 0)
GOTO on_error
END
COMMIT TRAN
RETURN (0)
on_error:
ROLLBACK TRAN
RETURN (-1)
GO
Note: The return values should be 0 for success and a negative number for failure.