SQL Server 2005 Books Online (BOL) explains the difference between the Seek Predicates and the WHERE Predicate: “The storage engine uses the index to process only those rows that satisfy the SEEK:() predicate. It optionally may include a WHERE:() predicate, which the storage engine will evaluate against all rows that satisfy the SEEK:() predicate (it does not use the indexes to do this).” In other words, SQL Server uses the Seek Predicates to traverse the index B-Tree from root to leaf level and to perform the partial ordered scan at the leaf level to find matches, then evaluates the WHERE Predicate against all matching rows that the Seek Predicates processed.
原文：https://www.cnblogs.com/WessonStar/p/13472013.html