November 2009
Intermediate to advanced
848 pages
30h 4m
English
book
SQL Server MVP Deep Dives
by Adam Machanic, Greg Low, Kimberly Tripp, Paul S. Randal, Kalen Delaney, Paul Nielsen
Content preview from SQL Server MVP Deep DivesBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Chapter 46. Using correlation to improve query performance
Gert-Jan Strik
SQL Server doesn’t keep statistics on the correlation between nonclustered indexes and the clustered index (with the exception of correlation information between datetime columns, if the DATE_CORRELATION_OPTIMIZATION setting is turned on). Instead, the optimizer assumes it has a low correlation; it assumes that a range of nonclustered index values is scattered all over the clustered index.
This assumption affects the optimizer’s decision whether or not to use the nonclustered index. If there is a high correlation, the optimizer will overestimate the cost of using the nonclustered index, which can cause it to disqualify the index from the query plan evaluation, resulting ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.