Databases Reference
In-Depth Information
To facilitate the conversion of LONG datatypes to LOBs, Oracle9
i
included support
for LOBs in most functions that support LONGs, as well as an option to the ALTER
TABLE statement that allows the automatic migration of LONG datatypes to LOBs.
BFILE
The BFILE datatype acts as a pointer to a file stored outside of the Oracle Database.
Because of this fact, columns or variables with BFILE datatypes don't participate in
transactions, and the data stored in these columns is available only for reading. The
file size limitations of the underlying operating system limit the amount of data in
a BFILE.
XMLType
As part of its support for XML, Oracle9
i
introduced a datatype called XMLType. A
column defined as this type of data will store an XML document in a character LOB
column. There are built-in functions that allow you to extract individual nodes
from the document, and you can also build indexes on any particular node in the
XMLType document.
Identity datatype
Oracle Database 12
c
introduces the identity datatype, which matches a datatype
found in IBM's DB2 database. This datatype is specifically designed to make it easier
to migrate applications that have used DB2 to Oracle.
User-defined data
Oracle8 and later versions allow users to define their own complex datatypes, which
are created as combinations of the basic Oracle datatypes previously discussed.
These versions of Oracle also allow users to create objects composed of both basic
datatypes and user-defined datatypes. For more information about objects within
Oracle, see
Chapter 14
.
AnyType, AnyData, AnyDataSet
Oracle9
i
and newer releases include three datatypes that can be used to explicitly
define data structures that exist outside the realm of existing datatypes. Each of
these datatypes must be defined with program units that let Oracle know how to
process any specific implementation of these types.
Type Conversion
Oracle automatically converts some datatypes to other datatypes, depending on the SQL
syntax in which the value occurs.
When you assign a character value to a numeric datatype, Oracle performs an implicit
conversion of the ASCII value represented by the character string into a number. For
instance, assigning a character value such as 10 to a NUMBER column results in an
automatic data conversion.
