Term: REF

Definition:
In Oracle PL/SQL, REF data types are pointers that uniquely identify a piece of data as an object. A reference can be established between an existent valid object and a table or type attribute using the REF pointer data type. An attribute referring to a nonexistent object leads to "dangling" situation. Note that a NULL object reference is different from a Dangling Reference.

To insert data into a ref column, the REF function is used to get an object instance reference.

Example Syntax:

[ATTRIBUTE | COLUMN] REF [OBJECT TYPE]

Example Usage:

The example code below shows the declaration of the REF attribute in table REFTAB. It points to TYPE_REFT object instance. Note the usage of REF as a function and the reference to an object instance.

CREATE OR REPLACE TYPE TYP_REFT AS OBJECT 

(A NUMBER, 

B NUMBER);

/



Type created.



CREATE TABLE REFTT OF TYP_REFT;



Table created.



CREATE TABLE REFTAB

(ID    REF    TYP_REFT);



Table created.



INSERT INTO REFTT VALUES (1,2);



1 row created.



INSERT INTO REFTAB

SELECT REF(T) FROM REFTT T



1 row created.



SELECT * FROM REFTAB;



ID

--------------------------------------------------------------------------------

00002202086F2A5BC83EC7440E97984B2C9EA9D9FEB2393991A58C4229897D0F775122F006