This tip is really simple but usefull if we're concatenating strings to write a Where clause.
For example:
DECLARE NVARCHAR @SQL = 'SELECT ... FROM ...'
IF(@IDAluno IS NOT NULL)
SET @SQL = @SQL + '' WHERE [IDAluno] = ' + CAST(@IDAluno AS NVARCHAR)
A better solution would be something like this:
SELECT ...
FROM ...
WHERE ([IDAluno] = @IDAluno OR @IDAluno IS NULL)
A special thanks to Paulo Moreira for the advice ;)