在Oracle SQL中是否存在类似“如果不存在创建序列…”的东西?

For my application that uses an Oracle 8 DB, I am providing an SQL script to setup stuff like triggers, sequences etc., which can be copied and pasted into SQL*Plus. I would like the script to not stop with an error if a sequence that I am trying to create already exists. For a Trigger this can easily be done using "create or replace trigger ...", but for a sequence this does not work. I also tried ""if not exists mysequence then create sequence ..." but it did not too. Is there some alternative?For my application that uses an Oracle 8 DB, I