CREATE FUNCTION [IF NOT EXISTS] function_name AS identifier [LANGUAGE JAVA|SCALA]
Create a user-defined function.
IF NOT EXISTS
If the function already exists, nothing happens.
LANGUAGE JAVA|SCALA
Language tag is used to instruct Flink runtime how to execute the function. Currently only JAVA and SCALA are supported, the default language for a function is JAVA.
Create a function named STRINGBACK.
create function STRINGBACK as 'com.dli.StringBack'