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Computed Columns: Reversing Data For Easier Searching

Last Updated January 19, 2018

Computed columns, Development, SQL Server

During Training We were talking about computed columns, and one of our students mentioned that he uses computed columns that run the REVERSE() function on a column for easier back-searching. What’s back-searching? It’s a word I just made up. The easiest example to think about and demo is Social Security Numbers. One security requirement is…

Sizing A New Server? Start With Maintenance.

Last Updated December 16, 2017

Backup and Recovery, CHECKDB and Corruption, First Responder Kit, SQL Server

Clientele Most of out customers are on slightly (ahem) older (AHEM) hardware, and they have big questions: How do we know what kind of hardware we need? How do we load test it? How do we know what to change to make it better? The load test question is interesting, particularly because getting a reliable…

Can you prevent deletes and inserts without a WHERE clause from running?

Last Updated December 12, 2017

Bad Idea Jeans, Humor

File this under bad idea thong In the tradition of Klaus Aschenbrenner wanting to prevent people from writing SELECT * queries, I thought it might be nice to prevent people from running deletes or updates without a WHERE clause. In a vaguely scientific way. Now, I don’t really condone this. It just seemed funny at…

Pocket Square

sp_BlitzQueryStore: A Gentle Introduction

Last Updated May 26, 2020

Execution Plans, First Responder Kit, Parameter Sniffing, Query Store (QDS), sp_BlitzQueryStore, SQL Server 2016, SQL Server 2017

Odds and ends During the precon, we asked how many people were on 2016, how many people were aware of query store, how many people were using it, and how many people were using sp_BlitzQueryStore. About 1/3 of the hands went up at first, then for each successive question, fewer and fewer hands stayed up.…

Partition Level Locking: Explanations From Outer Space

Last Updated November 22, 2017

Development, Locking, Blocking, and Isolation Levels, Partitioning

It’s not that I don’t like partitioning It’s just that most of my time talking about it is convincing people not to use it. They always wanna use it for the wrong reasons, and I can sort of understand why. Microsoft says you can partition for performance. Partitioning large tables or indexes can have the…

Implied Predicate and Partition Elimination

Last Updated December 4, 2017

Execution Plans

>implying Way back when, I posted about turning the Votes table in the Stack Overflow database into a Partitioned View. While working on related demos recently, I came across something kind of cool. It works for both partitioned tables and views, assuming you’ve done some things right. In this example, both versions of the table…

Partitioned Views, Aggregates, and Cool Query Plans

Last Updated December 4, 2017

Execution Plans

The Max for the Minimum Paul White (obviously of course as always) has a Great Post, Brent® about Aggregates on partitioned tables Well, I’m not that smart or good looking, so I’ll have to settle for a So-So Post about this. There are actually quite a few similarities between the way a partitioned table and…

Adaptive Blog Posts

Last Updated October 2, 2017

Adaptive Joins, Execution Plans

It turns out I can be dumb In a previous blog post about Adaptive Joins, I thought that EXISTS wasn’t supported by the new feature. It turns out that EXISTS is totally 100% supported, as long as your indexes support EXISTS. To show this, I need to show you a query that gets an Adaptive…

Live Query Plans and Blocking

Last Updated September 21, 2017

Execution Plans, Indexing, Locking, Blocking, and Isolation Levels, SQL Server

You’d think this would be cool After all, you’ve got a query plan being executed LIVE ON NATIONAL TELEVISION! But it’s not. It’s actually one of those weird reasons why you still need other ways of looking at DMVs for issues. Demo Library Let’s take a closer look! First, we need an index. Indexes are…

Optional Parameters and Missing Index Requests

Last Updated September 15, 2017

Execution Plans, Indexing, SQL Server

That’s when it all gets blown away At one point or another in everyone’s SQL-querying career, they end up writing a query that goes something like this: Transact-SQL SELECT something FROM stuff WHERE (@thing1 is NULL or whatever = @thing1) AND ... 1234 SELECT somethingFROM stuffWHERE (@thing1 is NULL or whatever = @thing1)AND ... These…

Indexing for Windowing Functions: WHERE vs. OVER

Last Updated March 12, 2018

Execution Plans, Indexing, SQL Server

Life Is Messy Demo queries have this nasty habit of being clean. Even using a pit of despair like Adventure Works or World Wide Importers, it’s easy to craft demo queries that fit the scenario you need to make yourself look like a genius. Stack Overflow, in all its simplicity, makes this even easier (lucky…

How Much Can One Column Change A Query Plan? Part 2

Last Updated September 8, 2017

Execution Plans, Indexing, SQL Server

What happened in Part 1? Join Elimination, naturally. Until the end. My copy of the Stack Overflow database doesn’t have a single foreign key in it, anywhere. If we go down the rabbit hole a couple steps, we end up at a very quotable place, with Rob Farley. 2. Duplicated rows Not necessarily duplicated completely,…

How Much Can One Column Change A Query Plan? Part 1

Last Updated September 3, 2017

Execution Plans, SQL Server

Beyond Key Lookups I’m going to show you two queries, and two query plans. The two queries are only different by one selected column, but the two query plans are wildly different. Unless I’ve talked to you in the last few days, these may surprise you as well. Here’s the first one. Transact-SQL DECLARE @DisplayName…

My Transaction Log File Is How Big?

Last Updated August 27, 2017

How bizarre So there’s this funny thing about SQL Server: many units of measure boil down to 8k pages. That’s the size of a data page, so when you measure reads, or size, sometimes the only thing you can do is convert that to MB or GB, or if you’re super lucky, TB. But transaction…

An Expensive Reason To Avoid AGs In Azure

Last Updated August 27, 2017

Always On Availability Groups, Backup and Recovery, CHECKDB and Corruption, Cloud Computing, High Availability, Microsoft Azure, SQL Server

Cash Rules Most people, when they get through paying for Azure, and SQL Server Enterprise Licensing, are left with a hole in their wallet that could only be filled with something that says “Bugatti”, and has a speedometer with an infinity sign at the end. Recently, while working with a client, I found out that…

Five Mistakes Performance Tuners Make

Last Updated July 27, 2017

Development, Execution Plans, Indexing, SQL Server

There’s no Top in the title And that’s because a TOP without an ORDER BY is non-deterministic, and you’ll get yelled at on the internet for doing that. This is just a short collection of things that I’ve done in the past, and still find people doing today when troubleshooting performance. Sure, this list could…

Chaining Agent Tasks For Alerting The Right Way

Last Updated August 4, 2017

Processes and Practices, Production Database Administration, SQL Server

Step By Step When you think about setting up maintenance, a persistent fear is that tasks may step on each other. You probably don’t want backups and CHECKDB and statistics maintenance running at the same time as statistics maintenance (notice I didn’t say index maintenance, here, because you’re smart and you skip it?). You may…

Locking When There’s Nothing To Lock

Last Updated July 27, 2017

Development, Execution Plans, Indexing, Locking, Blocking, and Isolation Levels

Demo Day We use StackOverflow for demos a lot. For all the reasons Brent mentions in his Great Post, Brent©, it’s pretty awesome. Where things get tricky is with locking demos. Sometimes the modifications can take a long time. This may be by design if you need to show long-held locks by sessions that aren’t…

ColumnStore Indexes And Recursive CTEs

Last Updated July 26, 2017

Columnstore Indexes, Indexing, SQL Server

Alone Together When I think about SQL Server features, I often picture a high school cafeteria. AGs are making fun of Mirroring, index rebuilds are walking around taking everyone’s lunch, dta is making a glue sandwich, and no one knows who Service Broker is even though they’ve been going to school together since Kindergarten. At…

Sliding Scale Parallelism: Why Stop At DOP?

Last Updated July 7, 2017

This is a thought experiment Just fair warning, you’re probably not going to learn anything new here. This also isn’t hidden in a CTP of SQL Server 2017, and as far as I know, it’s not a consideration outside of this post. Seriously, lawyers, I know nothing. I was just thinking (while sober, mind you),…