YQL

YQL, or Yahoo Query Language, was a powerful and innovative web service developed by Yahoo. It allowed users to query data from various sources, including web pages and APIs, using a SQL-like syntax. This meant that developers could retrieve and manipulate data from disparate sources as if it were a single database, greatly simplifying data integration tasks.

The core concept behind YQL was its ability to transform structured and unstructured data into a unified format. It utilized "tables" which were essentially wrappers around different data sources. For example, a table could be created to access Yahoo's Weather API, another to scrape data from Wikipedia, and yet another to query content from a Flickr album. Users could then write SQL queries that spanned these different tables, fetching and combining information from multiple origins in a single request.

YQL offered a significant advantage for web developers and data analysts by abstracting away the complexities of different API protocols and data formats. Instead of learning numerous individual APIs, developers could learn the YQL syntax and apply it to a wide range of data providers. This enabled rapid prototyping, data aggregation, and the creation of mashup applications. While YQL was a valuable tool, Yahoo eventually deprecated the service, leading to its discontinuation.