The Unwritten Rules of Power Query (that you're probably breaking)

Hey Data Enthusiast!

Does this sound familiar - you’ve created your query, but every time you hit refresh or make an update, it feels like an eternity before you see results? If you're nodding in agreement, you're not alone. Many of us have been there, realizing too late that our queries aren't built as efficiently as they could be. In Power Query, it's not just about what you do, but how you do it. Today we're revealing the lesser-known yet powerful rules of Power Query to transform your data handling into a swift, seamless process.

Please click here to download the practice file related to point 2 below.

1. Quick Operations Before Complex Ones 🚀:

Operations that do not require scanning the entire dataset should be your starting point. These tasks, like filtering, are generally faster and can make a substantial difference in efficiency. The key is to begin with simpler operations and save the more intensive ones for later.

👉 Example: Apply Filters Before Aggregations

When analysing a large dataset, such as global sales, apply a filter (e.g., to a specific region) before performing aggregations like sum or average. This reduces the amount of data being processed in the aggregation step, resulting in quicker execution.

👉 Example: Filtering Before Sorting

Consider a large dataset of sales records. If you begin with a sort operation, it will be slow as it has to process every record. A smarter approach is to first filter the dataset to a more manageable subset, like sales from a particular year. Then, when you apply sorting to this filtered data, it is much faster and more efficient.

2. Testing on a Smaller Dataset 🧪:

For complex queries, it's effective to test your steps on a smaller portion of your data. This allows for quicker iterations and troubleshooting.

👉 Example: Use a Subset of Data for Testing

Initially apply your steps to a small section of your data, like the first 100 rows. This helps you quickly identify and fix any issues. Once you're satisfied with the results, apply the same steps to the entire dataset.

Please click here to download the practice file.

Here are the steps to create your subset of data:

Once you’ve created your query and it’s proven to work, proceed to step 9:

📥Your Turn: Share Your Thoughts & Topic Wishes

Remember, in Power Query, the order in which you perform tasks can greatly impact processing time. Starting with less intensive tasks and saving the more demanding ones for later will streamline your data processing. In future weeks we will unveil more of these unwritten rules, please stay tuned!

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🏆 Comment of the Day

Please click here if you would like to check out the video that wayneedmondson1065 is referring to, it dives into automating your VLOOKUPs and fixing errors you may encounter when performing these lookups in Power Query.

Until next time, keep those queries rolling, and may your data always be clean and your transformations swift!

Happy Querying!

Thanks for reading. Until next week!

Miss Microsoft