Here’s a strange insight that I gained when building a test case where I needed some randomized values. In order to generate random values, you can use the NEWID() function, which creates a uniqueidentifier value for each row. But NEWID() comes with a strange behaviour, that some (including me) will consider a bug, while others (including the SQL Server development team) consider it to be “by design”.
There are three different perspectives when you look at a T-SQL statement; the way it’s written, the way it’s evaluated, and the way it’s executed. They’re all important to understand, for different reasons.