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Oracle PL/SQL Programming: A Developer's Workbook by Andrew Odewahn, Steven Feuerstein

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Chapter 9. Object Technology

Beginner

Q:

9-1.

All these statements are (or can be) true:

Suppose you want to keep track of your compact disc collection. Before the Oracle Objects option was available, you could have created a record type and some related procedures:

TYPE CD_rec_type IS RECORD (
   id     INTEGER,
   title  VARCHAR2(60),
   artist VARCHAR2(60),
   label  VARCHAR2(60)
);

PROCEDURE
set_cd_title
(cd_rec_in   IN OUT CD_rec_type,
 title_in    IN VARCHAR2)
IS ...

PROCEDURE
set_cd_artist
(cd_rec_in   IN OUT CD_rec_type,
 artist_in   IN VARCHAR2)
IS ...

With the Oracle Objects option you can bring together the data structure and its associated logic. You define an object type that encapsulates the CD data structure along with functions and procedures needed to manipulate the data.

  1. This CREATE TYPE statement defines object type CD_t:

    CREATE TYPE CD_t AS OBJECT (
       id     INTEGER,
       title  VARCHAR2(60),
       artist VARCHAR2(60),
       label  VARCHAR2(60),
       MEMBER FUNCTION
          set_title  (title_in    IN VARCHAR2)
             RETURN CD_t,
       MEMBER FUNCTION
          set_artist (artist_in   IN VARCHAR2)
             RETURN CD_t,
       MEMBER FUNCTION
          set_label (label_in     IN VARCHAR2)
             RETURN CD_t
    );
  2. CD_t is a data structure with attributes id, title, artist, and label, as well as methods set_title, set_artist and set_label. So CD_t defines both data (e.g., attributes ID, title) and behavior (e.g., methods set_title, set_artist).

  3. Same as (b).

  4. CD_t is also a template and can hold no data; it can be used simply to define object instances.

Q:

9-2.

All these statements are true. But (e) has a restriction, ...

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