T-SQL

Development, T-SQL

dba, development, performance tuning, sql server

I’d been meaning to write this for a while I half-stumbled on the weirdness around SQL_VARIANT a while back while writing another post about implicit conversion. What I didn’t get into at the time is that it can give you incorrect results. When I see people using SQL_VARIANT, it’s often in dynamic SQL, when they don’t…

Inline Table Valued Functions: Parameter Snorting

February 8, 2017

dba, development, performance tuning, sql server

You’ve probably heard about parameter sniffing But there’s an even more insidious menace out there: Parameter Snorting. It goes beyond ordinary parameter sniffing, where SQL at least tried to come up with a good plan for something once upon a compile. In these cases, it just plain gives up and throws a garbage number at…

High Compiles and Multi-Statement Table Valued Functions

January 26, 2017

SQL Server, T-SQL, TempDB

dba, development, performance tuning, sql server

Way back in 2016 I wrote about what to do if sp_BlitzFirst warns about high compiles. During GroupBy, Adam Machanic gave a great talk on new features in SQL Server 2016. It reminded me of a blog post I wanted to write about one common culprit of high compiles: Multi-Statement Table Valued Functions. Leaving aside…

Your Favorite Bugs & Enhancement Requests: #TSQL2sday 86 Roundup

January 17, 2017

I dunno about you, but I got a big stocking full of coal. Next year, I’m gonna be better, and I plan on asking Santa for a whole bunch of Connect requests. For T-SQL Tuesday, I asked you to name your favorite SQL Server bugs & enhancement requests, and here’s what you want in your…

#TSQL2sday: System-Maintained LastUpdatedDate, LastUpdatedBy Columns

January 10, 2017

#tsql2sday, t-sql tuesday

T-SQL

For this month’s T-SQL Tuesday, we’re talking about interesting Connect requests to fix or change SQL Server behavior. T-SQL Tuesday In our Senior DBA Class, one of the exercises involves figuring out changes to a table after an Always On Availability Group failover. In every class, several students always say the same thing: “I really…

Announcing T-SQL Tuesday #86: SQL Server Bugs & Enhancement Requests

January 3, 2017

#tsql2sday, t-sql tuesday

T-SQL

I know this is going to come as a stunning shock to you, dear reader, so you may want to be sitting down. SQL Server isn’t perfect. It’s okay. Deep, calming breaths. We’re going to get through this together, and here’s how: Go to Connect.Microsoft.com, the place where we file bug reports and enhancement requests…

A Little Fun With Math

November 18, 2016

I’ve never been much at math But I’ve always liked reading about it. It’s super interesting, and it always blows my mind. Like, guaranteed. Once in a while I’ll even try my hand at solving problems I read about in SQL. Not because SQL is a particularly good language for it; but just because sometimes…

What TRY/CATCH Doesn’t Handle

May 17, 2016

Tara Kizer

We were once asked in class what TRY/CATCH doesn’t handle besides object existence errors. It’s well documented in Books Online (BOL). If you’re like me, then tl;dr. Are we even calling it Books Online these days? I still say “bookmark lookup” instead of “key lookup”. I suppose I’ll be saying Books Online for quite some…

Another reason why scalar functions in computed columns is a bad idea

January 26, 2016

dba, sql server

As if there weren’t enough reasons In my last blog post I talked about different things that cause plans, or zones of plans, to execute serially. One of the items I covered was computed columns that reference scalar functions. We know that they’ll make queries go serial, but what about other SQL stuff? Oh no my…

Give Your T-SQL a Semicolonoscopy

December 17, 2015

In theory, all of your T-SQL statements are supposed to end with a semicolon, like this: Transact-SQL SELECT * FROM dbo.Posts; SELECT * FROM dbo.Comments; GO 123 SELECT * FROM dbo.Posts;SELECT * FROM dbo.Comments;GO Why? Well, SQL Server 2005’s Books Online says: Many code examples use a semicolon (;) as a Transact-SQL statement terminator. Although the…

Window Functions and Cruel Defaults

September 29, 2015

dba, development

My First Post Here… Well, my first technical post, was about how the default index creation method is OFFLINE. If you want that sweet, sweet Enterpri$e Edition ONLINE goodness, you need to specify it. It’s been a while since that one; almost six months to the day. So here’s another one! But Window Functions Are…

Indexing for Windowing Functions

June 17, 2015

Indexing, SQL Server, T-SQL

Hooray Windowing Functions They do stuff that used to be hard to do, or took weird self-joins or correlated sub-queries with triangular joins to accomplish. That’s when there’s a standalone inequality predicate, usually for getting a running total. With Windowing Functions, a lot of the code complexity and inefficiency is taken out of the picture,…

The Top 3 Mistakes T-SQL Developers Make

March 3, 2015

Doug Lane

Development, SQL Server, T-SQL

Over the years, I’ve done all kinds of awful things with T-SQL and made countless mistakes. Some were harmless; others were borderline catastrophic (exciting times!). I was curious what kind of horrible mistakes other people make, so I threw the question out to Twitter. Every answer I got was unique, which was both telling (so…

Are SQL Server Functions Dragging Your Query Down?

October 14, 2014

Jes Schultz Borland

Execution Plans, SQL Server, T-SQL

In most coding languages, functions are often-used blocks of code that can be reused from multiple locations, leading to less code – and cleaner code. SQL Server also lets us create functions that can be used the same way. They are reusable blocks of code that can be called from multiple locations. So, if you…

Refactoring T-SQL with Windowing Functions

March 31, 2014

Doug Lane

SQL Server, T-SQL, Videos

You’ve been querying comparative numbers like Year To Date and Same Period Last Year by using tedious CTEs and subqueries. Beginning with SQL Server 2012, getting these numbers is easier than ever! Join Doug for a 30-minute T-SQL tune-up using window functions that will cut down dramatically on the amount of code you need to…

How to Cache Stored Procedure Results

December 26, 2013

Say you run an online store, and on each item’s page, you need to show related items that people purchased. Let’s take an Amazon page for my favorite rechargeable AA batteries: Frequently Bought Together In a perfect world, we would cache this data in the web/app tier – but back here in the real world,…

Windowing Function Examples for SQL Server

July 14, 2011

Jeremiah Peschka

Aggregations and grouping can be a pain in the rear for the novice SQL developer. Way back in 2003, the ANSI/ISO standards people figured this out and added windows and ranking functions to the standard. In 2005, Microsoft added a few of these functions (ROW_NUMBER(), RANK(), DENSE_RANK(), and NTILE()) as well as the OVER() clause…

Well, it was good, but I dunno about amazing.

Seeks, Scans, and Statistics in the Grocery Store

May 10, 2011

Indexing, T-SQL

Building an execution plan is a lot like going shopping. Before I leave the house, I need to think about a few things: How many items do I need? I take a glance at my grocery list to see roughly how many things I’m shopping for. What stores am I going to visit? I can’t…

Sargability: Why %string% Is Slow

June 9, 2010