No duplicates

[slimdave]

apply a unique constraint. Here's some example constraints ...

create table
   my_table
      (
      col1 number primary key,
      col2 number unique,
      col3 references my_parent_table
      );


create table
   my_table
      (
      col1 number
         constraint
            xpkmy_table
         using index
            tablespace my_ts
            pctfree 0 nologging,
      col2 number
         constraint
            unq02my_table
         using index
            tablespace my_ts
            pctfree 0 nologging
       );

Now, go and read the SQL Reference, and the Concepts Guide, on the subject of constraints.