Any guides on learning how to interpret a SQL query's Execution Plan in SQL Server 2005?

Is there any good article, tutorial or similar references on interpreting the Execution Plan of a query in SQL Server 2005?

From stackoverflow

• Red Gate offers a free e-book on exactly this :)

  alextansc : Oh. My. God. Just browsing through e-book shows it contains a lot of information I've been looking for on execution plans. Thank you!