Database Reference
In-Depth Information
Note:
The BLOB, CLOB, and NCLOB datatypes are only available in
Oracle 8 and up. The LONG, RAW, and LONG RAW datatypes will even-
tually be removed in a future release in favor of the LOB datatypes. LOB
stands for “large object” or “binary large object.”
16.2.2
Reference Pointer Datatypes
A reference pointer datatype is used to point to a point in space. Nothing
Einsteinian is implied; the space exists only somewhere in an Oracle data-
base. The reference pointer datatype can be used to gain access to the value
referenced by the reference pointer. Reference pointer datatypes are shown
in Table 16.3.
Table 16.3
Oracle Reference Pointer Datatypes.
Datatype
Parameters
Example
BFILE
None
BFILE
Stores pointers to an external file, such as an audio track. Ora-
cle provides predefined functions for reading, storing, and
writing a BFILE column. Requires a directory object in order
to function.
REF
REF schema.objname
REF
MUSIC.INSTRUMENT_OBJ
Reference object identifier. Used for object tables to define a
referential or object-parent to another object table, similar to a
foreign key.
Note:
BFILE or BFILENAME pointers became available in Oracle 8 and
should be used in favor of any LONG or RAW datatypes.
A BFILE pointer is commonly used to store static multimedia objects.
Generally, unless multimedia objects are annotated or continually altered,
they can be considered static. A BFILE pointer only stores a reference to
an object such as an image. The image is stored external to the database
on disk. From a database perspective, storing multimedia outside the
database is the most efficient method available for both storage and subse-
quent access.
