Michael Swart (Database Whisperer) posted a great write up and interview with Brad Schulz that is worth checking out. Michael’s post links to a post from Brad on the use of EXIST and what is required for the SELECT portion of the statement.
Hope you are still with me.
Definitely worth the read and +1 for my blog subscriber list.
As he demonstrates, it doesn’t matter whether you use SELECT *, SELECT 1 or SELECT 1/0. If you want to know what this means, please read his post.
From SQL Server’s perspective, it doesn’t consider any of this information in preparing the results. The only thing that matters and this is from a practices perspective is to select a style for writing EXISTS statements and sticking to it.