Oracle PL/SQL/Table/DUAL Table

Do simple calculation by using dual

    
SQL>
SQL> select 123 * 456 from dual;
   123*456
----------
     56088
SQL>
SQL> select sysdate from dual;
SYSDATE
----------
26-10-2009
SQL>

SELECTING FROM DUAL

  
SQL>
SQL> DESC DUAL;
 Name                                                                                                                                    Null?    Type
 ----------------------------------------------------------------------------------------------------------------------------------------------- -------- ------------------------------------------------------------------------------------------------
 DUMMY                                                                                                                                            VARCHAR2(1)
SQL> SELECT * FROM DUAL;
D
-
X
1 row selected.
SQL>
SQL> SELECT 18*1.05 FROM DUAL;
   18*1.05
----------
      18.9
1 row selected.
SQL>
SQL> select "ABC" from dual;
"AB
---
ABC
1 row selected.
SQL>
SQL> select "A" || "B" from dual;
"A
--
AB
1 row selected.
SQL>

The DUAL Table

 
SQL>
SQL>
SQL> --The DUAL Table
SQL>
SQL> DESC dual;
 Name
 -----------------------------
 DUMMY
SQL>