DEREF

Syntax

Description of the illustration deref.gif

Purpose

DEREF returns the object reference of argument expr, where expr must return a REF to an object. If you do not use this function in a query, then Oracle Database returns the object ID of the REF instead, as shown in the example that follows.

Examples

The sample schema oe contains an object type cust_address_typ. The "REF Constraint Examples" create a similar type, cust_address_typ_new, and a table with one column that is a REF to the type. The following example shows how to insert into such a column and how to use DEREF to extract information from the column:

INSERT INTO address_table VALUES
  ('1 First', 'G45 EU8', 'Paris', 'CA', 'US');

INSERT INTO customer_addresses
  SELECT 999, REF(a) FROM address_table a;

SELECT address
  FROM customer_addresses
  ORDER BY address;

ADDRESS
--------------------------------------------------------------------------------
000022020876B2245DBE325C5FE03400400B40DCB176B2245DBE305C5FE03400400B40DCB1

SELECT DEREF(address)
  FROM customer_addresses;

DEREF(ADDRESS)(STREET_ADDRESS, POSTAL_CODE, CITY, STATE_PROVINCE, COUNTRY_ID)
--------------------------------------------------------------------------------
CUST_ADDRESS_TYP_NEW('1 First', 'G45 EU8', 'Paris', 'CA', 'US')