Jon Fletcher, Author at Purple Frog Systems

How to Handle Deleted Rows in an Incremental Load
September 4^th, 2026 in Big Data, Blog, Data Lakehouse, Data Warehouse, ETL, SQL, SQL Server, SSIS, Uncategorised
Most data warehouse issues are apparent: a pipeline fails, an alert fires, you get a phone call at an unsociable hour. Deleted source data doesn’t do this. A row is removed from the source, and no one notices. It sits in the warehouse silently skewing measures and KPIs, until the finance director asks why a cancelled order is still in the revenue report. What’s causing this? Incremental loads use watermarks to avoid re-extracting…
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Python Dictionaries – What do I need to know?
April 16^th, 2026 in Blog, Python
When you’re learning Python, dictionaries are one of the most important data structures you’ll encounter. Unlike lists (see blog post) which store items by position, dictionaries store data as key-value pairs, making them the natural choice whenever you need to look something up by name rather than by index. In this post, we’ll cover everything you need to know about Python dictionaries: what they are, how they work, and how to…
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Back Up and Restore a Fabric Lakehouse
November 27^th, 2025 in Backup, Blog, Fabric, Restore Point
Fabric Lakehouses have been around for a while, but they still offer no native way to back them up or restore them. Fortunately, the way Lakehouses are structured makes it possible to build your own backup process. A Lakehouse is split into two areas: Files and Tables. The Files area is straightforward, you can download and back up these items directly. The Tables are powered by Delta tables, which are made up of two key components: the…
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Python Lists – What do I need to know?
July 21^st, 2025 in Blog, Python
When you’re learning Python, lists are one of the first data structures you’ll encounter. They’re simple, powerful, and flexible. But what should you really know to use them effectively? In this post, we’ll cover everything you need to know about Python lists: what they are, how they work, and how to use them efficiently. What is a Python List? A list is a mutable, ordered, heterogeneous collection of items. Think of it as a…
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How to Effectively Restore a Table in a Fabric Warehouse
February 3^rd, 2025 in Backup, Blog, Fabric, Restore Point, Time Travel, Warehouse
If you’ve ever used a database, you’ve probably experienced that heart-jolting moment when you accidentally drop a table or run an update statement without a WHERE clause. In that instant, the table is either gone or potentially corrupted beyond repair. Fortunately, there are ways to recover data, depending on the environment you’re working in. In traditional databases like on-prem SQL Server, or other systems that rely on physical…
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My Experience at Fabric Community Conference Europe 2024
October 1^st, 2024 in Blog, Data Lakehouse, Data Warehouse, Fabric, Power BI
Stockholm: A city of charm and innovation Let’s start with the location, Stockholm. As a seasoned traveller, Stockholm is one of the few major European cities that I have not yet visited. So, when given the chance to go to FabCon Europe, I jumped at the chance. Stockholm is a great city, with beautiful historic architecture mixed with modern innovation and the people there were friendly and warm. The conference centre, the Stockholmsmässan,…
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Upload files to a LakeHouse in OneLake using Powershell
January 12^th, 2024 in Azure, Blog, Fabric, OneLake, Power BI
In this blog post, I will be sharing a PowerShell script that uploads files to a OneLake Lakehouse. This is the script: The script is downloadable at the bottom of the page as a txt file. To use the script there are few steps: Install the Powershell module Az.Storage. This code exists in the script and just needs to be uncommented for the first run, if the module is not already installed. Fill in the variables at the top of the script: tenantID…
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How to combine images using Python
September 19^th, 2023 in Blog, Python
In this blog post, I will be showing how to combine images using Python. I used this code in a for loop to combine hundreds of different images for one of our clients. These are the two images that we will combine. Pillow is a PIL fork, install Pillow using pip and import PIL into the Python script. Next, set the two variables. These images are saved in the same folder as the script, therefore only the filenames are required to reference them.…
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How to add text to images using Python
March 13^th, 2023 in Blog, Just For Fun, Python, Uncategorised
In this blog post, I will be showing how to add text to an image in Python. I used this code to generate hundreds of images with different text for one of our clients. The full script is downloadable at the bottom with the required extras. Firstly, install the Python library Pillow. Pillow is a PIL fork, install Pillow using pip and import PIL into the Python script. In Python, select the image that you would…
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SQL Server Agent Gantt Chart in Power BI
December 22^nd, 2022 in Blog, Power BI, PowerBI, SQL Server
In this blog post, I walk-through how to use a Power BI template file I have created that displays a Gantt chart which shows which SQL Server Agent Jobs have run and when. The purpose of the chart is to identify when jobs are overlapping and taking server resource off each other. If two or more resource intensive jobs overlap, it’s a good idea to schedule them at different times if possible. To use the template file, input the server name.…
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