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Day: December 7, 2022

Distinct Counts in KQL

Published 2022-12-07 by Kevin Feasel

Robert Cain continues a series on KQL:

In an earlier post in this series, Fun With KQL – Count, you saw how to use the count operator to count the number of rows in a dataset.

Then we learned about another operator, distinct, in the post Fun With KQL – Distinct. This showed how to get a list of distinct values from a table.

While we could combine these, it would be logical to have a single command that returns a distinct count in one operation. As you may have guessed by the title of this post, such an operator exists: dcount.

Read on to see how you can use dcount in queries, including how you can perform speed versus accuracy trade-offs.

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InvalidAbfsRestOperationException in Synapse Managed VNet

Published 2022-12-07 by Kevin Feasel

Kamil Nowinski goes down a rabbit hole:

This happens on the customer’s Synapse workspace where we have a public network disabled, so only private endpoint and managed VNET are available. Additionally, you probably spotted, that it took over 3 minutes to actually get this message. Hence, as a next step, in order to minimize the potential causes I simplified the query to make sure I have access to the Storage, by listing the files:

Click through for a story of pain, followed by glorious resolution.

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Semi-Colons in Snowflake

Published 2022-12-07 by Kevin Feasel

Kevin Wilkie punctuates the statement:

With our last blog post, we started discussing Snowflake and the SELECT statement. Now, if you remember, there is this great thing called a semi-colon.

The main reason you should use the semicolon is to terminate all of your queries. Snowflake does this great thing by default, letting you run one query at a time.

I remember back when Microsoft deprecated T-SQL statements which did not end with semi-colons. It was fun speculating for about 5 minutes regarding the carnage which would happen if they carried out the deprecation notice, not least of which we’d find in Microsoft-developed code.

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Tracking Database Errors with Extended Events

Published 2022-12-07 by Kevin Feasel

Eitan Blumin is watching you:

But interestingly enough – we would be getting an added benefit here. Even if there is no SQL injection attack, it’s still possible that such errors would be raised by the application – simply due to bugs.

Furthermore, these errors in the database may be happening without anyone even noticing! How could that be, you ask? Well, it could be due to bad error handling that “swallows” the error entirely, or because the errors are logged but no one is bothering to look at the logs, or maybe because the errors are caught but an undetailed error message is logged/displayed to the user (I can’t even count how many times I encountered “general database error” messages in applications), or because the developers simply decided to mark this as a “known issue” that they didn’t bother to fix and they didn’t think to ask their DBA about it… The reasons are numerous and varying.

Click through for the scripts. I had built something similar about a decade ago, a simple WPF app which watched for errors. I messaged him with something like “You missed a comma in that IN clause” and I saw him pop up from his cubicle and look around, trying to figure out how I could peek over his shoulder and see the query.

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In Praise of Stored Procedures

Published 2022-12-07 by Kevin Feasel

Jay Robinson defends the highly defensible:

The point I’m trying to make is that the database code is treated as part of the solution. It is in the repos just like the C# code. It is deployed just like the C# code. I even include unit testing, just like the C# code.

I also keep all T-SQL in the database. There is no T-SQL code inside the C# code. Stored procedures are used for all functionality, even basic CRUD functions. In fact, probably 80–90% of the stored procedures in my systems are essentially CRUD functions. The only operation that doesn’t go through stored procedures is bulk insertion, and I use SqlBulkCopy for that.

Jay makes what I often consider the most important point from the standpoint of developers: that stored procedures act as an interface.

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