Execution plans show you what's going on behind the scenes in SQL Server. They can provide you with a wealth of information on how SQL Server is executing your queries, including the points below.
- Which indexes are getting used, and where no indexes are being used at all.
- How the data is being retrieved, and joined, from the tables defined in your query.
- How aggregations in GROUP BY queries are put together.
- The anticipated load, and the estimated cost, that all these operations place upon the system.
All this information makes the execution plan a fairly important tool in the tool belt of database administrator, database developers, report writers, developers, and pretty much anyone who writes T-SQL to access data in a SQL Server database.
Given the utility and importance of the tool, you'd think there'd be huge swathes of information devoted to this subject. To be sure, fantastic information is available from various sources, but there isn't one place to go for focused, practical information on how to use and interpret execution plans.
This is where my book comes in. My goal was to gather into a single location as much useful information on execution plans as possible. I've tried to organize this information in such a way that it provides a clear route through the subject, right from the basics of capturing plans, through their interpretation, and then on to how to use them to understand how you might optimize your SQL queries, improve your indexing strategy, and so on.
