Learn T-SQL Querying

How query processing impacts plan reuse

It's important to contextualize what happens in terms of query processing that can result in plan caching and reuse. In this section, we will focus on the highlighted sections of the following diagram, which determine whether a query plan can be reused from the cache or needs to be recompiled:

As mentioned, when an incoming T-SQL statement is parsed, a query hash value representing that statement as it was written is generated, and if that query hash is already mapped to a cached query plan, it can just attempt to reuse that plan unless special circumstances exist that don't even allow plan caching, ...