Comparing Nullable Columns

Daniel Hutmacher shows an elegant way to compare multiple nullable columns on two tables:

Because we’ve added OR conditions into the mix, we’re forced to use the Nested Loop join, which loops over table B for every single row in A. That’s a lot of index scans and it comes with a hefty price tag.

Here’s an absolutely eye-watering beautiful pattern that I found on the Interwebs (though I forgot where) the other day.

This is an interesting use of INTERSECT.  Check it out.

Shortest Paths

Kevin Feasel



Sanjay Mishra and Arvind Shaymsundar tie R to SQL Server to solve a pathfinding problem faster:

In such a case, if a developer were to implement Dijkstra’s algorithm to compute the shortest path within the database using T-SQL, then they could use approaches like the one at Hans Oslov’s blog. Hans offers a clever implementation using recursive CTEs, which functionally does the job well. This is a fairly complex problem for the T-SQL language, and Hans’ implementation does a great job of modelling a graph data structure in T-SQL. However, given that T-SQL is mostly a transaction and query processing language, this implementation isn’t very performant, as you can see below.

The important thing to remember is that these technologies tend to complement each other rather than supplant them.

Azure SQL Data Warehouse GA

Kevin Feasel



James Serra notes that Azure SQL Data Warehouse is now generally available:

In brief, SQL DW is a fully managed data-warehouse-as-a-service that you can provision in minutes and scale up in seconds.  With SQL DW, storage and compute scale independently.  You can dynamically deploy, grow, shrink, and even pause compute, allowing for cost savings.  Also, SQL DW uses the power and familiarity of T-SQL so you can integrate query results across relational data in your data warehouse and non-relational data in Azure blob storage or Hadoop using PolyBase.  SQL DW offers an availability SLA of 99.9%, the only public cloud data warehouse service that offers an availability SLA to customers.

The pricing calculator now reflects GA prices.

Desired Enhancements

Jason Brimhall has a list of some nice SQL Server updates and bug fixes, followed by some things he’d like to see:

Digging a little deeper on this one. I would really love to see an enhancement to Resource Governor. Not just any enhancement will do. I need it to be enhanced so it will also affect the reporting services engine and the integration services engine in addition to the database engine. I want to be able to use RG to prevent certain reports from over consuming resources within the SSRS engine. Or for that matter, I want to make sure certain SSIS packages do not consume too much memory. If I can implement constraints on resources for these two engines it would be a huge improvement.

Check it out.


Kyle Kingsbury looks at VoltDB:

Unlike most SQL databases, which default to weaker isolation levels for performance reasons, VoltDB chooses to provide strong serializable isolation by default: the combination of serializability’s multi-object atomicity, and linearizability’s real-time constraints.

Serializability is the strongest of the four ANSI SQL isolation levels: transactions must appear to execute in some order, one at a time. It prohibits a number of consistency anomalies, including lost updates, dirty reads, fuzzy reads, and phantoms.

If you use VoltDB, it sounds like upgrading to 6.4 is a good idea.

Out With SQLPS

Mike Fal casts out SQLPS and looks at new and updated Powershell cmdlets:

An important facet of the provider is that it behaves like a file system. How many of us have deleted files from the command line? Have you also used a PowerShell one-liner to delete old files, like backups? If you have, you might be familiar with two parameters: -WhatIf and -Confirm. These two switch parameters are extremely helpful because they can keep you from cutting yourself with that sharp PowerShell knife.

With the July 2016 update, the SQL Server provider now supports the use of these two switches. While using them may not be a common situation, it’s good to know that they are there. After all, it could be handy if you wanted to clean up some items from the command line, like maybe a junk database. Now you can both check what you’re going to do before you do it, along with getting a confirmation question when you go for the actual delete:

I am a huge fan of the -WhatIf switch, so that gets a thumbs up from me.

SSMS And Azure SQL Data Warehouse

Rob Farley reports that we can now use Management Studio to connect to Azure SQL Data Warehouse:

One of the biggest frustrations that people find with SQL DW is that you need (or rather, needed) to use SSDT to connect to it. You couldn’t use SSMS. And let’s face it – while the ‘recommended’ approach may be to use SSDT for all database development, most people I come across tend to use SSMS.

But now with the July 2016 update of SSMS, you can finally connect to SQL DW using SQL Server Management Studio. Hurrah!

…except that it’s perhaps not quite that easy. There’s a few gotchas to be conscious of, plus a couple of things that caused me frustrations perhaps more than I’d’ve liked.

Yes, it’s never quite that easy…  Read the whole thing.

When Servers Behave Differently

Grant Fritchey tells a tale of two servers which behave quite differently when running the same query:

Now what?

Well obviously something somewhere is different. Start by comparing everything on both servers and both databases down to… hang on, here, we’ll write a PowerShell script and then….

Wait, wait, wait!

You have the execution plans? Before we start digging through all the properties everywhere and comparing everything to everything, updating statistics 14 times, and all the rest, what if we look at the execution plans. They’re different, so we should start looking at scans & indexes & statistics &….


Sometimes, it’s the little things that matter.

A Wish For Shutdown Procedures

Dave Mason wants shutdown procedures like how we can have startup procedures:

If ‘shutdown’ was valid for the @OptionName parameter, I know exactly what I’d do: configure sp_procoption to execute a stored proc that sends an email alert. It would be great to know when a SQL instance goes down, wouldn’t it? Looking at the log file, we can see entries indicating the instance was shut down:

Dave does mention potential failure scenarios, but I agree:  it’d be nice to have the ability to run procedures at shutdown to perform certain actions.

Using Biml To Load From Flat Files

Ben Weissman shows how to use Biml to load data from XML files:

To make use of flat files, Biml will require one or more flat file formats as well as the corresponding flat file connections. A flat file connection is nothing but a link between a flat file format and the path to a flat file. While in real life, you might rather want to loop across multiple files using the same format, we’ll keep it simple for now and assume that we’ll have one file per format (which is the case here anyway due to our AdventureWorks sample data).
For reasons of readability and also the ability to easily reuse our code, we’ll make use of a new extension method called GetFlatFileFormatfromXML. If you have not read our post on creating your own extension methods, you may want to do that first.

Getting the extension method in place is about 90% of the solution.  Read on to see the whole thing.


February 2019
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