select nbr_ssn
from data_exch.t_exch_data_header d
left join data_exch.t_exch_match_header m
            on d.idn_header_data_exch = m.idn_header_data_exch;


Operation                Name                   Rows    Bytes   Cost    CPU Cost   IO Cost
SELECT STATEMENT                                35M     640M    113506  16G        112293 
 HASH JOIN RIGHT OUTER                          35M     640M    113506  16G        112293 
  INDEX FAST FULL SCAN   PK_T_EXCH_MATCH_HEADER 1752K   10M     1722    251M       1703 
  PARTITION HASH ALL                            35M     438M    61548   8G         60932 
    TABLE ACCESS FULL    T_EXCH_DATA_HEADER     35M     438M    61548   8G         60932 




select nbr_ssn
from data_exch.t_exch_data_header d
inner join data_exch.t_exch_match_header m
            on d.idn_header_data_exch = m.idn_header_data_exch
union all
select nbr_ssn
from data_exch.t_exch_data_header d
where not exists (
            select *
            from data_exch.t_exch_match_header m
            where d.idn_header_data_exch = m.idn_header_data_exch
);


Operation                  Name                 Rows    Bytes   Cost	CPU Cost   IO Cost
SELECT STATEMENT                                35M     641M    227011  16G        112293 
  UNION-ALL
   HASH JOIN                                    1752K   31M     113506  16G        112293 
    INDEX FAST FULL SCAN   PK_T_EXCH_MATCH_HEAD 1752K   10M     1722    251M       1703 
    PARTITION HASH ALL                          35M     438M    61548   8G         60932 
     TABLE ACCESS FULL     T_EXCH_DATA_HEADER   35M     438M    61548   8G         60932 
   HASH JOIN RIGHT ANTI                         33M     609M    113506  16G        112293 
     INDEX FAST FULL SCAN  PK_T_EXCH_MATCH_HEAD 1752K   10M     1722    251M       1703 
     PARTITION HASH ALL                         35M     438M    61548   8G         60932 
      TABLE ACCESS FULL    T_EXCH_DATA_HEADER   35M     438M    61548   8G         60932