Function : dump

Purpose
DUMP returns a VARCHAR2 value containing the datatype code, length in bytes, and
internal representation of expr. The returned result is always in the database character
set.
The argument return_fmt specifies the format of the return value and can have any
of the following values:
■ 8 returns result in octal notation.
■ 10 returns result in decimal notation.
■ 16 returns result in hexadecimal notation.
■ 17 returns result as single characters.
By default, the return value contains no character set information. To retrieve the
character set name of expr, add 1000 to any of the preceding format values. For
example, a return_fmt of 1008 returns the result in octal and provides the character
set name of expr.
The arguments start_position and length combine to determine which portion
of the internal representation to return. The default is to return the entire internal
representation in decimal notation.
If expr is null, then this function returns NULL.
This function does not support CLOB data directly. However, CLOBs can be passed in
as arguments through implicit data conversion.

eg：
SQL>select dump('ORACLE',10) from dual;
DUMP('ORACLE',10)
-------------------------------
Typ=96 Len=6: 79,82,65,67,76,69

SQL>select dump('ORACLE',10,4,2) from dual;
DUMP('ORACLE',10,4,
-------------------
Typ=96 Len=6: 67,76

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