R. C. van Dijk (8/24/2009)
I totally agree that this is what should be done first! That is even one of the biggest reasons why we always want access to the production systems of our clients!However, taking (only) this approach causes you to miss out on any possible functional issues there might be (e.g. to much data being shown or processed by the client(s) ).
Taking a step back and looking at the big picture forces you to look at all possible sides of the problem. Taking a techie approach is just not always the way to go.
How are you going to decide if 'too much' data is being shown to the client? And what good is it going to do to say "no longer return these 10 columns" if that doesn't make the query run perceptibly faster? Unless ntext or nvarchar(max) columns are being returned and unused due to a sloppy "select *" (which you should almost never have in production code) trimming columns isn't likely to solve the reported business problem of the query being slow. "Runs too slow" seems an entirely techie problem to me.