In SQL Server, the cost of a particular plans is based largely on I/O, which makes this post a good candidate for this month’s T-SQL Tuesday, hosted by Mike Walsh who, like me, walks a straight path. In considering I/O – the movement of data generally In and Out of disk and memory – my thoughts come very much to query cost. If I run set ...

Author: Thomas Kejser Reviewers: Juergen Thomas, Sanjay Mishra, Stuart Ozer, Lubor Kollar, Kevin Cox, Kun Cheng In this blog, we will provide additional details on a well-hidden feature in SQL Server 2008 – partition-level locking. But before we illustrate the feature, here’s a bit of background about lock escalation and lock granularities. ...

Lots of blog posts for this month, for the first T-SQL Tuesday to leave the safe-haven of Adam Machanic’s blog. Some people obviously missed out, probably because they don’t read this blog, but I guess that’s the nature of the meme. I don’t know who is hosting next month yet, but I’ll be looking out for Adam to post ...

I’m feeling the pressure for this month’s T-SQL Tuesday, probably because I’m also the host. I’ll be posting a roll-up for it soon too, which I’m sure will be great fun researching. Given that the topic is on relationships, and the main SQL Server database is a relational engine, relationships are incredibly relevant ...

It’s time for the third of Adam Machanic’s T-SQL Tuesdays, and this time, I’m the host. The first one, last December was on the topic of date/time, and the second was on Puzzling Situations. Check them both out, along with the round-ups that Adam wrote about them. Lots of great topics, which is starting to make me anticipate the ...

A recent discussion on Twitter about a query that Denny Cherry was looking at led to this post by Josef Richberg: http://josef-richberg.squarespace.com/journal/2010/1/28/is-a-case-statement-considered-sargable.html, and I thought it might be worth going through a few points on the topic of SARGability. Particularly given that I wrote a related ...

SARGable is an adjective in SQL that means that an item can be found using an index (assuming one exists). Understanding SARGability can really impact your ability to have well-performing queries. Incidentally – SARG is short for Searchable ARGument. If you have an index on phone numbers using LastName, followed by FirstName, including the suburb ...

Earlier today you may have seen a blog post of mine about a puzzle involving HAVING. You should read that post before this one. It was part of Adam Machanic’s T-SQL Tuesday meme. The question was about the query: SELECT 'No Rows' WHERE 1=2 HAVING 1=1; And here’s the explanation. Start by making yourself a "dual table", ...

Adam’s hosting another T-SQL Tuesday, for which this post is jumping in. He’s themed it around T-SQL Puzzles, which I found quite interesting, because the world is full of them. Most of the questions that I answer on forums, help sites, and so on, are puzzles. I guess there’s the difference between “Problem” and “Puzzle”, but I prefer to think of ...

Foreign Keys are great. For those of you who read some of my other posts, or heard me present on this material before, a foreign key can really help the Query Optimizer simplify out your query, because it knows that it must be able to find a match in an equality join (unless the field allows NULLs, which is a whole nother story). I also blogged ...