I always thought of them as synonymous, however I think Oracle
would like to move solely to distinct.
this is what Oracle says:
DISTINCT | UNIQUE
Specify DISTINCT or UNIQUE if you want Oracle to return
only one copy of each set of duplicate rows selected
(these two keywords are synonymous).
Duplicate rows are those with matching values for each expression
in the select list.
Restrictions on DISTINCT and UNIQUE Queries
When you specify DISTINCT or UNIQUE, the total number
of bytes in all select list expressions is limited to the size
of a data block minus some overhead.
This size is specified by the initialization parameter DB_BLOCK_SIZE.
You cannot specify DISTINCT if the select_list contains LOB columns.
you can lead someone to something but they will never learn anything ...