How to Extract Data from Paginated Websites Using PowerQuery

Extracting data from websites that spread information across multiple pages can be challenging. This step-by-step guide demonstrates how to efficiently collect data from paginated websites using PowerQuery in Excel, with a practical example of gathering information about the largest companies by market capitalization.

Understanding the Pagination Challenge

When dealing with websites that distribute data across multiple pages, manually extracting information from each page is time-consuming and inefficient. For instance, if you need to extract data about the top 500 companies by market cap, and each page displays 100 companies, you would need to process five different pages.

Identifying URL Patterns

The first step is to understand how the URL changes between pages. In our example, the URL structure includes a page number parameter that increments with each page (e.g., changing from ‘page=2’ to ‘page=3’). This pattern is crucial for automating the data extraction process.

Creating a Function in PowerQuery

To extract data from multiple pages efficiently, follow these steps:

1. Open Excel and navigate to the Data tab
2. Select ‘From Web’ and paste the URL of the first page
3. After connecting to the website, identify the relevant table from the navigator (in this case, table three)
4. Select ‘Transform Data’ to open the PowerQuery Editor
5. Access the Advanced Editor to modify the query

Converting the Query to a Function

The key to handling pagination is converting your query into a function that accepts a page number as a parameter:

1. In the Advanced Editor, identify the URL in your code
2. Replace the hardcoded page number with a parameter
3. Structure the function to build the URL dynamically based on the input page number

This transformation allows you to invoke the function with different page numbers to retrieve data from specific pages.

Processing Multiple Pages

To extract data from a range of pages:

1. Use the List.Transform function to apply your custom function to a list of page numbers
2. Create a list of required page numbers (e.g., {1..5} for pages 1 through 5)
3. Apply the function to each page number in the list

Combining the Results

The final step is to merge all the individual page results into a comprehensive dataset:

1. Use Table.Combine to concatenate all the tables returned from different pages
2. This creates a single table containing data from all specified pages

Customizing the Range

A significant advantage of this approach is its flexibility. By simply adjusting the range of page numbers in your list, you can extract data from as many pages as needed. Whether you need data from 5 pages or 50, the process remains the same.

This powerful technique enables efficient data collection from paginated websites, saving time and reducing the potential for errors that come with manual data extraction methods.