Press "Enter" to skip to content

Author: Kevin Feasel

Finding Foreign Key Relationships in SQL Server

Published 2020-02-04 by Kevin Feasel

John Morehouse shows how you can piece together foreign key relationships in SQL Server:

Recently, I had to purge some parent records from a table.  In this case, the parent table had foreign keys, which itself isn’t an issue.  The fact that there were more than 30 of them was.   While SQL Server will happily tell you that you are violating a foreign key if a child record is present when deleting the parent record, finding all of them can be cumbersome.  This is even more true when you have a larger number of foreign keys.

Thankfully, SQL Server can tell us a lot of information about foreign keys including both the parent and child tables as well as the column used.  From this information, we can dynamically create a SELECT statement that would tell us the number of child records that are tied to the parent ID.

Click through for the solution.

Comments closed

Splitting Strings with T-SQL

Published 2020-02-04 by Kevin Feasel

Andy Levy recommends using STRING_SPLIT():

Last year, you finally retired the last of your SQL Server 2008R2 instances. Congratulations! But are you taking advantage of everything that your new instances have to offer? Unless you did a review of all of the T-SQL in your applications, I’m guessing not.

At one time or another, we all find ourselves having to do some string parsing, especially splitting strings on a delimiter. Nearly all of us have one (or two or a dozen) functions for doing this somewhere on every instance of SQL Server. But since SQL Server 2016, we’ve had an official way to do it – the STRING_SPLIT() function.

Andy’s example involves splitting strings, but there are plenty of functions which come into the T-SQL lexicon. It might be worth doing a quick review of the available system functions just to see if there’s something useful which slipped with a newer version of SQL Server.

Comments closed

SQL Server and Query Costs

Published 2020-02-04 by Kevin Feasel

Jared Poche explains some of the ideas behind the costing algorithm in SQL Server:

One thing to remember is that cost in SQL Server is always an estimate. This is a number SQL Server calculates when considering multiple potential plans to determine which would be the best. But the number of rows it expects a given operation to return or how many times that operation runs can be off. All of that is based on statistics.

It doesn’t then go back and update the cost number later if those numbers were incorrect. So while we can use the cost as an indicator of which query or operator we should focus on, don’t completely tunnel-vision that one thing.

This kind of cost mismatch allows something to look awful on an execution plan but not actually be a problem, or (in the case of most user-defined functions prior to SQL Server 2019) vice versa.

Comments closed

Burn the Database Down

Published 2020-02-04 by Kevin Feasel

Jana Sattainathan has a script to drop almost all user objects in a database:

I hope this script does not become infamous for the wrong reasons! Please use caution.

I had to help a team recreate everything in a database and test their scripts but leave the roles and role grants in place. Basically, this meant that I could have scripted out the permissions and recreated the database but I thought it would be easier and more re-runnable to just drop everything else except the permissions.

Caution here means making sure you have good backups beforehand, ensuring that you pick the right database, and double-checking everything.

Comments closed

Big Data Clusters and Fixed IP Addresses

Published 2020-02-04 by Kevin Feasel

Denny Cherry warns you about Big Data Clusters and keeping a particular IP address:

No problem, we just added in the correct IP range to the possible addresses for the vNet, added a new Subnet and moved the VMs over to the new subnet (which caused the VMs to reboot, but that was expected).

It turns on that BDC in SQL Server 2019 doesn’t like having the IPs changed for the aks nodes.  The problem stems from the fact that BDC is generating its certificates off of the IP address of the node, so if the IP address of the node changes (even if you are using DHCP for on-prem nodes and DHCP gives you a new IP address) your BDC won’t respond.

Read on for your three possible solutions.

Comments closed

Generating Fake Data with R

Published 2020-02-03 by Kevin Feasel

Dave Mason takes a look at generating fake PII in R:

I’ve been thinking about R and how it can be used by developers, DBAs, and other SQL Server professionals that aren’t data scientists per se. A recent article about generating a data set of fake transactional data got me thinking about this again and I wondered, can R be used to obfuscate PII data?

In a word, yes. Well, mostly. (More on this in a bit.) As with anything R-related, there are probably multiple packages that are useful for any given task. For this one, I’ll focus on the “generator” package.

Click through to see what it does and Dave’s thoughts on the topic. It would also be possible to generate fake data in R by hitting a web API like Daniel Hutmacher’s service.

Comments closed

Fun with Palindromic Dates

Published 2020-02-03 by Kevin Feasel

Tomaz Kastrun has a bit of fun with the date February 2, 2020:

As of writing this blog-post, today is February 2nd, 2020. Or as I would say it, 2nd of February, 2020. There is nothing magical about it, it is just a sequence of numbers. On a boring Sunday evening, what could be more thrilling to look into this little bit further 🙂

Let’s kick R Studio and start writing a lot of useless stuff.

Tomaz also compares US versus EU palindromic dates and visualizes the different distributions.

Comments closed

Updating the Powershell Kernel in Azure Data Studio Notebooks

Published 2020-02-03 by Kevin Feasel

Bob Pusateri has a two-parter on Powershell notebooks. First up is the problem:

PowerShell Notebooks are a great new feature in Azure Data Studio, first becoming available in the November 2019 release. Like SQL notebooks, PowerShell notebooks are based on Jupyter Notebooks format, which are interactive documents containing text and executable code blocks.

Having some working PowerShell code that I wanted to share along with explanations and examples, I created a PowerShell Notebook. The only problem was my functions would never initialize. Actually they would never stop initializing – I would run the cell they were defined in, and it would just keep running forever.

And then Bob has the solution:

It turns out I did not have the latest version of the PowerShell Kernel running on my machine. The latest version is currently 0.1.3, and I had 0.1.2. Upgrading appears to have solved this issue for me – yay!

This solution also raises the issue that there is no notification from Azure Data Studio that a PowerShell Kernel exists or is in need of updating. I (and probably others) will just believe that as long as Azure Data Studio is up to date, we’re good to go. So how does one update their PowerShell kernel? Well, it’s simple, but not intuitive.

Read on to see how.

Comments closed