load data in power query it does not sort

3 min read 23-01-2025

load data in power query it does not sort

Power Query, a powerful data integration and transformation tool, often surprises users with its behavior regarding data sorting upon import. Many expect data to automatically sort upon loading, but this isn't the default behavior. This article explains why Power Query doesn't automatically sort data and provides solutions for achieving your desired sorting order.

Understanding Power Query's Approach to Data Loading

Power Query prioritizes data integrity and efficiency over automatic sorting. Loading data without sorting is significantly faster, especially with large datasets. Sorting is a resource-intensive process that can slow down the initial data load. Power Query assumes you might want to perform other transformations or filters before sorting, allowing for more flexible data manipulation.

Why Data Doesn't Sort Upon Loading in Power Query

Performance: Large datasets require significant processing power to sort. Power Query avoids this to provide a snappy initial loading experience.
Flexibility: Sorting too early could hinder other transformations. You might need to filter or merge data before deciding on the optimal sorting order.
Data Integrity: Power Query aims to preserve the original data structure and order. Sorting changes the order, which can be undesirable in some scenarios.

How to Sort Data in Power Query

Despite its initial lack of automatic sorting, Power Query provides several ways to sort your data after import:

1. Using the "Sort" Feature in the Power Query Editor

This is the most straightforward method.

Load your data: Import your data source into Power Query.
Open the Power Query Editor: After loading, click "Edit" or "Transform Data" to open the editor.
Select the column to sort by: Click the column header you want to sort.
Access the "Sort" function: Go to the "Transform" tab in the ribbon. Find and click the "Sort Ascending" or "Sort Descending" button. This will sort your data in the selected column.

Note: You can sort by multiple columns. Just repeat steps 3 and 4 for additional columns, specifying the order (ascending or descending) for each.

2. Sorting During Data Import (Advanced)

For advanced users, you can incorporate sorting directly into the data import process using M code. This allows for more complex sorting logic or sorting based on multiple criteria. However, this method requires familiarity with the Power Query formula language (M). An example (sort by "Column1" ascending):

let
    Source = Csv.Document(File.Contents("C:\your_file.csv"),[Delimiter=",", Columns=4, Encoding=65001]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Column1", type text}, {"Column2", type number}, {"Column3", type text}, {"Column4", type date}}),
    #"Sorted Rows" = Table.Sort(#"Changed Type",{{"Column1", Order.Ascending}})
in
    #"Sorted Rows"

Replace "C:\your_file.csv" with your actual file path, adjust column names and data types accordingly.

3. Adding a Sort Step to a Pre-Existing Query

If you're working with an existing query, you can easily add a sort step. Just add a new step after the initial data import step using the methods described above. This preserves your previous query steps while allowing you to sort.

Troubleshooting Common Sorting Issues

Data Types: Ensure the column you're sorting is of the correct data type (e.g., numbers, text, dates). Incorrect data types can lead to unexpected sorting results.
Null Values: Power Query handles null values in different ways depending on the sort order. Experiment with different methods and parameters to get the desired results.
Advanced Sorting: For complex sorting requirements, including custom sorting algorithms, you'll need to utilize M code within the Power Query editor.

By understanding the reasons behind Power Query's default behavior and utilizing the methods explained above, you can easily sort your data after loading and achieve your desired data organization. Remember that prioritizing data integrity and efficiency is paramount, and sorting is a flexible step that comes after the initial load.