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Using Object IDs
(OIDs) in Oracle
Oracle Tips by Mike Ault |
Using REFs
A REF value is the OID (Object Identifier) for
an Object instance. An object identifier is a unique identifier
(supposedly global, but how this is guaranteed is not clear) that
uniquely identifies the object being REFed. Another thing to notice
is the rebirth of the DUAL table. Dual is a single column single
value table that was used by triggers and procedures in late version
6 and some version 7 but then fell out of use. Now with OIDs it is
being used again. Be sure to watch out for duplicate values getting
into DUAL as this will break your code if DUAL is used. Even though
a method is capable of reading another objects data, a method should
use messaging to other methods. In a true object oriented
environment a method will only affect data inside its own object.
Therefore two methods will be required to establish an association,
one to request the REF and one to pass it. An example of this use of
types and OID is shown in listing 1.
CREATE OR REPLACE TYPE
address_t AS OBJECT (
street VARCHAR2(30),
city VARCHAR2(30),
state CHAR(2),
zip CHAR(5))
/
CREATE OR REPLACE TYPE emp_t AS OBJECT (
employee_id INTEGER ,
name name_t,
birthdate DATE,
hiredate DATE,
address address_t,
dependents dependent_list,
SEE CODE DEPOT FOR FULL SCRIPTS
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