Skip to main content

SQL Server: Checking @@ROWCOUNT and @@ERROR

The following SQL contains a subtle bug that will always result in the text “No Rows Affected” being output.

SELECT 'Hard Coded Row'
IF(@@ERROR <> 0)
Print 'Error Occured'
ELSE IF(@@ROWCOUNT = 0)
Print 'No Rows Affected'

The error occurs because the reference to @@ERROR in the first “IF” statement counts as a SQL statement; resetting the value held in @@ROWCOUNT.   As the second “IF” statement checking @@ROWCOUNT is only evaluated if the first “IF” statement (@@ERROR) it will always return true!   Note: Reversing the order of the two IF statements would hide any potential errors, as @@ERROR would be reset upon checking @@ROWCOUNT.

The safest way to evaluate this statement is to SELECT the contents of @@ERROR and @@ROWCOUNT into local variables within a single statement and then check the values of the local variables, in other words:

DECLARE @ErrorCode INT
DECLARE @RowsAffected INT

SELECT 'Hard Coded Row'
SELECT @ErrorCode = @@ERROR, @RowsAffected = @@ROWCOUNT

IF(@ErrorCode <> 0)
Print 'Error Occured'
ELSE IF(@RowsAffected = 0)
Print 'No Rows Affected'

Problem solved!

Comments

Post a Comment

Popular posts from this blog

Why do my Android Notification only appear in the status bar?

I'm definitely getting back into Android development, I'm remembering that feeling of 'Surely this should be easier than this!'. All I wanted to do was to schedule a local notification which behaved similar to a push notification pop-up. That is, as well as showing the small icon in the status bar I wanted it to pop up on screen to notify the end user. All seems fairly easily, I found this code for how to schedule a notification. That all worked perfectly, apart from the notification would only appear in the status bar. Searching around I found loads of different answers / solutions, mostly all saying the same thing:It only worked if you used 'NotificationCompat.Builder' in place of 'Notification.Builder', orYou had to set the priority to 'NotificationCompat.PRIORITY_HIGH'As usually happens, none of these solutions worked for me until I added in the missing piece of the jigsaw:- '.setDefaults(Notification.DEFAULT_ALL)'. For me this…

IPhone hangs when running from XCode

I've had this happen a couple of times now and the first time was a little worrying that I'd bricked my iPhone. Basically I was running an application on my phone via XCode and when rebuilding an updated version it failed with a "busy" error message. Stopping XCode and unconnecting my phone had no effect, the phone was stuck displaying the loading screen of the application and wouldn't respond to any key commands. To fix you have to hard reboot, holding the power and home button until the phone reboots - doesn't lose any of the data you have on your phone (a concern the first time I did it).

Do "Task Hours" add anything in Scrum (Agile)?

What do task hours add to the overall process in scrum?This was a question that has arisen from all team members in both instances that I've helped teams switch over to scrum. The benefits of artifacts like the comparative story point estimation, the 2 week sprints, stand-ups and the end of sprint demo have been self evident to the team, but as one I think every team member has expressed dismay when it comes to task planning and estimating each task in hours. Left unchecked there is a natural tendency for people to actually begin to dread the start of each sprint purely due to the task planning session.In my current role we've been lucky to investigate this further as a team.The team sat down to discuss the problems it was experiencing with estimating tasks in hours and the following common themes appeared:It is hard: Maybe it shouldn't be, but time estimation is hard! Story points are comparative and abstracted making them easier to determine, but time estimate is gen…