Teradata Database provides a wide range of built-in functions that address many of the needs of typical users. In those cases when standard functions are inadequate, Teradata Database allows you to define user-defined functions (UDFs) that extend the capability of normal SQL within the database.
UDFs are database objects that you build or acquire. For example, you can install UDF objects or packages from third party vendors without providing the source code. A UDF is similar to standard SQL functions such as SQRT, ABS, or TRIM and is invoked in the same manner.
You can write UDFs in C or C++, then compile them into shared objects. Once compiled, you can use the UDF in SQL statements for activities such as enforcing business rules or aiding in the transformation of data.