Hi

Actually what happens when we issue create database command Oracle automatically creates the tablespace and tables using the sql.bsq script found in the $oracle_home/rdbms/admin directory this scripts the dual table and is owned by the sys and has one column and one row.

hello

dual is a table which is created by oracle along with the data dictionary.
It consists of exactly one column whose name is dummy and one record.
The value of that record is X.

sql> desc dual
Name Null? Type
----------------------- -------- ----------------
DUMMY VARCHAR2(1)

sql> select * from dual;

D
-
X

The owner of dual is SYS but dual can be accessed by every user.
As dual contains exactly one row (unless someone fiddled with it)
it is guaranteed to return exactly one row in select statements if a
constant expression selected against dual such as in:

select sysdate from dual

Although it is possible to delete the one record or insert additional records
one really should not do that!.

thnaks
Ashish Sharma