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