Our MVP buddy Erland Sommarskog doesn't post articles that often but when he does, you should read them. His latest post is here: http://www.sommarskog.se/query-plan-mysteries.html It talks about why a query might be slow when sent from an application but fast when you execute it in SSMS. But it covers way more than that. There is a great deal of good info on how queries are executed and query plans generated. Highly recommended!...(read more)