DUAL IS A DUMMY TABLE. WE CAN INSERT,UPDATE AND DELETE FROM DUAL TABLE IF YOU LOG IN WITH SYSTEM/MANGER PRIVILLAGES.

EXAMPLE:

SELECT * FROM DUAL;
no rows selected


DESC DUAL
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 DUMMY                                              VARCHAR2(1)


SQL> INSERT INTO DUAL VALUES('Y');

1 row created.


SQL> SELECT * FROM DUAL;

D
-
Y


SQL> UPDATE DUAL SET DUMMY='S';

1 row updated.

SQL> SELECT * FROM DUAL;

D
-
S


SQL> DELETE FROM DUAL;

1 row deleted.

SQL> SELECT * FROM DUAL;

no rows selected


EVEN IF U INSERT A ROW INTO DUAL TABLE STILL IT CAN BE USED TO RETRIEVE DATA FOR PSUEDO COLUMNS.

YOU CAN INSERT ONLY ONE RECORD INTO THE DUAL TABLE, IF U TRY TO INSERT ANOTHER RECORD IT WILL NOT GIVE ANY ERROR,IT WILL JUST DISPLAY 1 ROW INSERTED BUT U WILL FIND ONLY 1 ROW. ie THE PREVIOUS RECORD.


REGARDS
SHARAT