When Microsoft® SQL Server™ completes the execution of a Transact-SQL statement, @@ERROR is set to the value 0 if the statement executed successfully. If an error occurs, an error message is returned. @@ERROR returns the number of the error message until another Transact-SQL statement is executed. You can view the text associated with an @@ERROR error number in the sysmessages system table.

Because @@ERROR is cleared and reset on each statement executed, check it immediately following the statement being validated or save it to a local variable that can be checked later.