Which of these data types is typically most difficult to query?

Unstructured data is indeed the type that is typically the most difficult to query. This is primarily because unstructured data lacks any predefined format or organization, making it challenging to analyze and interpret using traditional query methods. This type of data includes formats like text documents, images, audio, and video files, which do not follow a specific schema. As a result, extracting meaningful insights from unstructured data often requires advanced techniques such as natural language processing, machine learning algorithms, or specialized tools designed to handle such data types.

In contrast, structured data is highly organized and easily searchable, residing in fixed fields within a record or file, such as in databases where data is typically stored in rows and columns. Semistructured data, while not as rigid as structured data, still contains some organizational properties that make it easier to process compared to unstructured data; examples include JSON or XML files. Formatted data refers to data that has been organized in a specific structure for easy access, making it more straightforward to query than unstructured data.