UDF

UDF is an acronym that can refer to several concepts. The two most common uses are Universal Disk Format, a file system for optical media, and User-Defined Function, a function created by a user in software and databases.

Universal Disk Format is a file system specification developed by the Optical Storage Technology Association to enable data interchange on optical media such as CDs, DVDs, and Blu-ray discs. It supports large files, long file names (including Unicode), and cross-platform compatibility across Windows, macOS, and Linux. UDF defines the structures for files and directories and supports multiple revisions adapted to newer media.

User-Defined Function refers to a function created by a user to perform a task within a programming language or database system. UDFs encapsulate logic, promote reuse, and simplify complex queries or calculations. They can be scalar (returning a single value) or table-valued (returning rows). Implementations exist in various SQL dialects such as T-SQL, PL/pgSQL, and PL/SQL, and may also be written in host languages. Considerations include performance, determinism, side effects, and security. In databases, UDFs can be used in SELECT statements, filters, or within views and procedures, depending on the system.