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What is Power Query?

Power Query, also known as the M language, is Microsoft's data connectivity and transformation technology embedded in Power BI, Excel, Azure Data Factory, and other Microsoft data products. Introduced in 2013 as a Power BI component, it provides a functional language for defining ETL (Extract, Transform, Load) pipelines that connect to hundreds of data sources and reshape data for analysis. The M language is a case-sensitive, functional language with lazy evaluation, where transformations are expressed as a series of let-in steps that build upon each other in a readable, sequential format.

Power Query's visual query editor generates M code through point-and-click operations, making it accessible to business analysts who may not write code directly, while power users can edit the underlying M expressions for advanced scenarios. Query folding is a key optimization feature where Power Query translates M operations back into the source system's native query language (like SQL), pushing computation to the data source rather than loading all data locally. The language supports custom functions, parameterized queries, error handling, and recursive operations for complex data transformation scenarios.

Power Query connects to databases, REST APIs, web pages, files, SharePoint lists, and dozens of other sources through built-in and custom connectors. Dataflows in Power BI Service and Azure Data Factory use Power Query Online for cloud-based data preparation. The technology has become central to Microsoft's self-service data preparation strategy, empowering millions of analysts to clean and transform data without IT involvement.