The concept of an SQL user-defined function (UDF) is important for understanding SAS In-Database processing because it is the very mechanism that enables work from SAS programs to be executed inside the DBMS. A UDF is simply a packaged routine that can be invoked from SQL statements. Most DBMSs provide a framework for packaging code into executable modules, storing them inside the database, and making them available to clients of the DBMS. In short, UDFs make it possible to extend the SQL semantics implemented by the DBMS. More information about how UDFs implement SAS In-Database processing is presented later on.
