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Day: December 1, 2020

Understanding Decision Trees

Published 2020-12-01 by Kevin Feasel

Ram Tavva walks us through the algorithm to design decision trees:

A decision tree is made up of several nodes:

1.Root Node: A Root Node represents the entire data and the starting point of the tree. From the above example the
First Node where we are checking the first condition, whether the movie belongs to Hollywood or not that is the
Rood node from which the entire tree grows
2.Leaf Node: A Leaf Node is the end node of the tree, which can’t split into further nodes.
From the above example ‘watch movie’ and ‘Don’t watch ‘are leaf nodes.
3.Parent/Child Nodes: A Node that splits into a further node will be the parent node for the successor nodes. The
nodes which are obtained from the previous node will be child nodes for the above node.

Read on for an example of implementation in R.

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The Effects of Undersampling and Oversampling on Predicted Probability

Published 2020-12-01 by Kevin Feasel

Bryan Shalloway has an interesting article for us:

In classification problems, under and over sampling techniques shift the distribution of predicted probabilities towards the minority class. If your problem requires accurate probabilities you will need to adjust your predictions in some way during post-processing (or at another step) to account for this.

Bryan has a clear example showing this problem in action.

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Measuring Powershell Profile Load Times

Published 2020-12-01 by Kevin Feasel

Jeffrey Hicks shows us how to keep track of lost time:

Here’s the “issue” that often arises. Someone will mention that PowerShell, and this includes PowerShell Core, takes too long to load. In fact, PowerShell now shows you how long it took to load. Almost always, the issue is something profile related. Sometimes a command is taking too long to run, or maybe the profile needs a little cleanup. I know my PS7 load times were high until I cleaned up a few items and re-structured some of the commands.

To make this easier, I put together a simple script that you can run in Windows PowerShell, or PowerShell (even cross-platform) that will run your profile scripts and report how long they take to complete.

Click through for more details, as well as a script to test how quickly your Powershell profiles load.

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JSON Basics with SQL Server

Published 2020-12-01 by Kevin Feasel

Steve Jones takes us through querying straightforward JSON data in SQL Server:

Recently I saw Jason Horner do a presentation on JSON at a user group meeting. I’ve lightly looked at JSON in some detail, and I decided to experiment with this.

All in all, I’ve been pretty happy with the syntax for JSON manipulation in T-SQL. I’m not the biggest user of JSON around, but when I’ve needed to slice or build JSON, even when I needed to build it in a certain way to emulate an old application, it has worked for me.

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Reducing CTE Re-Scans with APPLY

Published 2020-12-01 by Kevin Feasel

Daniel Hutmacher shows another good use of the APPLY operator:

You can tell by the plan why this is an inefficient query: the SQL expression in the common table expression is executed once for every time that it’s referenced in the code.

Better living through CROSS APPLY

You could store the results of the CTE in a temp table, but where’s the fun in that? Instead, why not use the CTE once, and then return four rows for each row that the CTE spits out? That’s exactly what CROSS APPLY does.

Read the whole thing and appreciate that much more all the nice things you can do with APPLY.

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Setting a Default Database for SQL Server Logins

Published 2020-12-01 by Kevin Feasel

Adrian Buckman shows us an issue with using a database other than master for a SQL Server login’s default:

This is one of them little options that I see which quite often gets little consideration or gets set to a user database without consideration of what the consequences may be if that DB becomes unavailable. There are going to be situations where setting a default other than master is essential and there are going to be situations where leaving as master suits best and this comes down to the individual requirements of each login, Recently I had to fix an issue with user connectivity for a single login, the user was getting failed connections when trying to connect to the SQL server when trying to access one of their legacy databases , everything appeared fine – User account was enabled the password hadn’t been changed and was therefore correct, the database they were trying to access was up and accessible but the SQL error log highlighted the real issue.

Click through for more details.

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Running Azure SQL Edge on Kubernetes

Published 2020-12-01 by Kevin Feasel

Andrew Pruski isn’t satisfied with one Raspberry Pi:

I’ve been playing around with Kubernetes for a while now and things like Azure Kubernetes Service are great tools to learn but I wanted something that I’d built from the ground up.

Something that I could tear down, fiddle with, and rebuild to my heart’s content.

So earlier this year I finally got around to doing just that and with Azure SQL Edge going GA with a disconnected mode I wanted to blog about my setup.

Click through to see how to do this.

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