1* alter table emp add constraint pk1 primary key (empno) using index tablespace tools
scott@9i > /

Table altered.

scott@9i > select index_name,table_name,tablespace_name from user_indexes where table_name='EMP';

INDEX_NAME                     TABLE_NAME                     TABLESPACE_NAME
------------------------------ ------------------------------ ------------------------------
PK1                            EMP                            TOOLS