Oracle8 datafiles setting

I confused the oracle datafile setting:

create database datafile...
create tablespace .... datafile ....
alter database create datafile....
alter database datafile....
alter tablespace ... add datafile ....

which commands are used when the datafile is not exist and need to create?
which commands are used when the datafile is already exist ?

Ken Received on Mon Jul 17 2000 - 00:00:00 CDT