Drop database only if Backup is successful - sql

Question

This might be an easy one for some one but I haven't found a simple solution yet.
I'm automating a larger process at the moment, and one step is to back up then drop the database, before recreating it from scratch.
I've got a script that will do the back up and drop as follows:
Use [Master]
BACKUP DATABASE [databaseName]
TO DISK='D:\Backup\databaseName\20100122.bak'
ALTER DATABASE [databaseName]
SET SINGLE_USER
WITH ROLLBACK IMMEDIATE
DROP DATABASE [databaseName]
but I'm worried that the DROP will happen even if the BACKUP fails.
How can I change the script so if the BACKUP fails, the DROP won't happen?
Thanks in advance!

Answer 1

If your SQL Server version is 2005 or greater, you can wrap your statements with a try catch. If the backup fails, it will jump to the catch without dropping the database...
Use [Master]
BEGIN TRY
BACKUP DATABASE [databaseName]
TO DISK='D:\Backup\databaseName\20100122.bak'
ALTER DATABASE [databaseName]
SET SINGLE_USER
WITH ROLLBACK IMMEDIATE
DROP DATABASE [databaseName]
END TRY
BEGIN CATCH
PRINT 'Unable to backup and drop database'
END CATCH

Answer 2

You can catch any error codes that occur with the SQL server error variable as follows. A zero indicates no error occurred. Note that the value is set every time a T-SQL statement is executed, so you need to catch it as soon as you have backed up:
USE [Master]
DECLARE #errorCode int
BACKUP DATABASE [databaseName]
TO DISK='D:\Backup\databaseName\20100122.bak'
SET #errorCode = ##ERROR
IF (#errorCode = 0)
BEGIN
ALTER DATABASE [databaseName]
SET SINGLE_USER
WITH ROLLBACK IMMEDIATE
DROP DATABASE [databaseName]
END
This is the simplest way I can think of, as well as allowing you to catch known error codes and handle them differently if you need to. SELECT * FROM master.sys.messages gives you a list of all known error codes and messages if you want to take it further.