Is it possible with just "SQL"

Question

Hi everyone,
I have a LOCAL TABLE with the following structure ..
EX:
TABLE_ID 1
EMPNO 1234
LAST_NM JOHN
FIRST_NM SMITH
DOB 06/05/1982
I have another TABLE which is in TRASACTIONAL DATABASE (which has million rows)
I have access to this table with a database link..
EX:
EMPNO 1234
LAST_NM JOHN
FIRST_NM SMITH
DOB 06/05/1982
I am trying to write a query which search for EMPLOYEE last_nm... But first it has search in the LOCAL TABLE if it doesnt find over there it hase hit the TRANSACTIONAL TABLE and get the   results back
EX:
If i search for LAST_NM as "JOHN"... I have JOHN in the LOCAL TABLE.. so the output would be like the following..
TABLE_ID EMPNO LAST_NM FIRST_NM DOB
1 1234 JOHN SMITH 06/05/1982
But if search for LAST_NM as "FORD".... I dont have it in the LOCAL TABLE..so the output would be like the following..
TABLE_ID EMPNO LAST_NM FIRS_NM DOB
NULL 5435 FORD STEVE 08/09/1973
If i dont give any search parameter ..it has give the output of all the employees in the LOCAL_TABLE....
IS it Possible to do With Just a SQL query..without using any PL/SQL....
Thanks in advance for the help
phani

Answer 1

SELECT *
FROM local_table
WHERE last_name = 'JOHN'
UNION
SELECT *
FROM remote_table
WHERE NOT EXISTS ( SELECT 1
FROM local_table
WHERE last_name = 'JOHN' ) AND last_name = 'JOHN' ;{code}