How to catch and handle only specific Oracle exceptions? From this and this i guess, that there is no predefined Named System Exceptions for ORA-00955. 

How can I rewrite the following to catch only the error ORA-00955?

begin
      EXECUTE IMMEDIATE 'CREATE SEQUENCE S_TEST START WITH 1 INCREMENT BY 1';
exception when OTHERS then
    Null;
end;


BTW Is there any syntax to catch errors by just providing the error-codes?
You have two options:



Refer to the exception directly by number:

 

BEGIN
    EXECUTE IMMEDIATE 'CREATE SEQUENCE S_TEST START WITH 1 INCREMENT BY 1';
EXCEPTION
    WHEN OTHERS THEN
      IF SQLCODE = -955 THEN
        NULL; -- suppresses ORA-00955 exception
      ELSE
         RAISE;
      END IF;
END; 




Other option is to use EXCEPTION_INIT Pragma directive to bind a known Oracle error number to user defined exception;



DECLARE
   name_in_use exception; --declare a user defined exception
   pragma exception_init( name_in_use, -955 ); --bind the error code to the above 
BEGIN
    EXECUTE IMMEDIATE 'CREATE SEQUENCE S_TEST START WITH 1 INCREMENT BY 1';
EXCEPTION
    when name_in_use then
       null; --suppress ORA-00955 exception
END; 





  BTW Is there any syntax to catch errors by just providing the error-codes?


Yes, I've demonstrated it in the first example

Further reading for variations on this:


Oracle Reference Documentation on Handling PL/SQL Exceptions