Yes, Foreign Keys Help Performance

SQL Server
I created this example several years ago that illustrates how foreign key constraints can help performance. It's a contrived example. Granted. I feel like it illustrates the point. However, over the years, people have questioned one aspect of it. The optimizer uses the foreign keys to figure out which tables can be eliminated from the query, making for a more efficient plan and making the query run faster. The pushback has always been, "Yeah, Grant, but nobody writes T-SQL where they include extra tables that they don't need." My initial response, after I stop laughing, is to point out any number of ORM tools. But, you know what, let's assume that's correct. No one would ever create a giant catch-all view that has all their JOINs in one place so they don't have…
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SQL Server Query Performance Tuning

SQL Server, T-SQL
The latest update to my book, SQL Server Query Performance Tuning was released last week. This is the fourth edition of the book, and the third edition that I've been responsible for. At the urging of my editor, Jonathan Gennick, I have completely restructured the book for this release. The chapters have been broken up and rearranged so that they're smaller, more easily consumed. Yes, I've worked with my technical editor, Joe Sack, to add lots of new information and to ensure that the existing information is more accurate and more useful. But, we've also added new chapters on topics that weren't given enough attention in the previous versions of the book, such as parameter sniffing. It can certainly seem like these book releases are just some incremental changes on top of…
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