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>