This post lists some options that you might consider if you need to do an indexed lookup of values that are longer than SQL's 900 bytes limit on index keys.
An overview of some concepts that are important to understand when examining query plans or troubleshooting slow queries.
You may find reference material on the Internet that says don't depend on expression short circuiting in T-SQL except in CASE statements. It turns out that there are edge cases where even CASE doesn't provide deterministic short circuit behavior.
User-defined data types (UDTs) in T-SQL seem alluring, but in reality they may fail to live up to their promise.
Query Hash Statistics is a free download that collects historical query and query plan fingerprint statistics and allows you easily to view the data in SSMS. It allows you to see the true cumulative cost of the queries in each of your databases, without a Profiler trace. You can use the project as-is, or – if you’re the tinkering type – disassemble it and build your own custom query hash stats solution. Source code is included.