Users complain about a timeout but when you run the exact same query in SSMS it runs in a flash. Sounds familiar? I've been baffled by this before. I worked out that I was getting a different query plan in SSMS because of different SET OPTIONS but, having dealt with that, I was then stuck with parameter sniffing as the cause of the timeout. I've read about that but still didn't really understand how to fix it. Erland Sommarskorg has published an excellent article (http://www.sommarskog.se/query-plan-mysteries.html) in which he clearly explains what's going on and provides tools and techniques to fix it. Highly recommended reading. Thanks, Erland.