SQL Guide : Using SQL for database administration : Managing indexes : Creating an index on a table
  
Creating an index on a table
CREATE [UNIQUE] INDEX index_name ON base_table_name
column_identifier
[ASC | DESC]
[, column_identifier [ASC | DESC]] ...
Only the creator of the particular table or users having SYS_ADMIN_ROLE have privileges to create or drop indexes.
The following example creates an index named X_TEST on column I of the table TEST.
CREATE INDEX X_TEST ON TEST (I);
See also
Managing indexes