Description of the illustration create

CREATE [ OR REPLACE ] FUNCTION [ schema. ] function_name
  [ ( parameter_declaration [, parameter_declaration]... ) 
  ]
  RETURN datatype
  [ { invoker_rights_clause
    | DETERMINISTIC
    | parallel_enable_clause
    | RESULT_CACHE  [ relies_on_clause ]
    }...
  ]
  { { AGGREGATE | PIPELINED }  USING [ schema. ] implementation_type
  | [ PIPELINED ] { IS | AS } { [ declare_section ] body 
                              | call_spec
                              | EXTERNAL
                              }
  } ;