Which function allows users to access data stored in a database?

Query functions are critical in accessing data stored in a database because they enable users to request specific information from the database using structured queries. These functions typically utilize a query language, such as SQL (Structured Query Language), which allows users to specify the data they want to retrieve, along with conditions and formats.

By using query functions, users can filter, sort, and aggregate data effectively, resulting in tailored outputs that meet their needs. This access is fundamental to database management systems, as it empowers users to interact with vast amounts of information, retrieve insights, and manipulate data with precision.

Other choices, while related to data processing, do not primarily focus on the access aspect. Data visualization tools are designed for presenting data in graphical formats, data import tools facilitate bringing data into a database, and data compression techniques are used to reduce the size of the data for storage efficiency. None of these functions inherently allow for querying or accessing data directly from a database as query functions do.