Answer / saraswathi muthuraman

Oracle will have a default table called 'DUAL'.
Dual table will have only one column "DUMMY". U cann't
insert values into dual table. By default, a row will
existing in dual table.

SQL> desc dual;
DUMMY varchar2(1)

SQL> select * from dual;

X

1 row selected.

SQL> insert into dual values (10);
insert into dual values (10)
*
ERROR at line 1:
ORA-01031: insufficient privileges


U can create you own table with the name of dual.

SQL> create table dual(xy number,zz number);

Table created.

SQL> desc dual;
xy number
zz number

u can insert values in you own dual table.

Answer / eshwari

Dual table is a sample permanent table which come along with
oracle.
for example if u want to knw the sin(45) value then u have
to retreave it from a table.but there is no table to
retreave that value.
so we use the sample table dual as table name in place of
table name in the select query.

ex:select sin(45) from dual;

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