CREATE OR ALTER FUNCTION
Creates a stored function if it does not exist, or alters a stored function
DSQL
CREATE OR ALTER FUNCTION funcname
  [ ( [ <in_params> ] ) ]
  RETURNS <domain_or_non_array_type> [COLLATE collation]
  [DETERMINISTIC]
  {<psql_function> | <external-module-body>}
!! See syntax of CREATE FUNCTION for further rules !!
The CREATE OR ALTER FUNCTION statement creates a new stored function or alters an existing one.If the stored function does not exist, it will be created by invoking a CREATE FUNCTION statement transparently.If the function already exists, it will be altered and compiled (through ALTER FUNCTION) without affecting its existing privileges and dependencies.