Dynamic API Query Construction

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The following Power Query (M) script demonstrates how to extract a list of dates from a table, convert them into a formatted string, and use them dynamically in an API request:

Step-by-Step Guide

let 
// Load the table containing relevant dates 
Source = DateTable, 
// Extract dates as a list 
DateList = Source[Date], 
// Convert list to a single comma-separated string 
DateString = Text.Combine(List.Transform(DateList, Text.From), ","), 
// Construct the API URL dynamically 
BaseUrl = "https://api.example.com/get/history?access_key=" & API_Key & "&dates=", 
FinalUrl = BaseUrl & DateString, 
// Fetch data from API 
ApiResponse = Json.Document(Web.Contents(FinalUrl)) 
in 
ApiResponse

Explanation:

  • Extracts a list of dates from the DateTable column.
  • Transforms each date into text format.
  • Combines the list into a single string separated by commas.
  • Builds a dynamic API request URL including the date parameters.
  • Retrieves data using the API request.

Application in get.myhistory

This approach can be used within get.myhistory to dynamically retrieve historical records by supplying a list of relevant dates. The function can operate on specific time intervals, allowing:

  • Efficient tracking of data changes over time.
  • Comparison of records across multiple periods.
  • Enhanced flexibility for querying historical data.

By integrating this logic into get.myhistory, you can automate the retrieval of historical snapshots based on predefined date intervals, making it a powerful tool for auditing and analysis.

Summary

This method showcases how lists can be dynamically converted into API query parameters, enabling efficient historical data retrieval.

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