A method is provided for generating a user-defined function (UDF) on a database engine of a database server. A user-function is sent to the database engine. The user-function includes a relational declaration with application and query logic. When the database engine receives the user-function, the database engine generates a function shell. The UDF processes the relational declaration of the user-defined function. The UDF includes the user-function and the function shell. The function shell returns a final data result of the user-defined function through the shell from the database engine.