Java Programming with Oracle SQLJ

4.2. Object Columns and Object Tables

You can use object types to define columns in a table. Such columns are known as object columns because they contain objects rather than scalar values. You can also define tables so that each row in the table represents an instance of an object. Such tables are known as object tables. In this section, you will learn to create both object columns and object tables. You will learn how to add, retrieve, and modify rows containing object columns, and how to add, retrieve, and modify rows in object tables.

4.2.1. Object Columns

An object column is a column in a table that is defined using an object type. (Objects stored in an object column are sometimes referred to as column objects.) The following example creates a table named customers. It contains one object column named customer, which is defined using the t_customer object type:

CREATE TABLE customers (
  customer t_customer
);

The customer column in this table is used to store objects of the t_customer type. You can see the structure of the table from SQL*Plus by entering the command DESC customers. For example:

SQL> DESC customers;
 Name                Null?   Type
 ------------------ -------- ----------------------------
 CUSTOMER                    T_CUSTOMER

Notice in this example that a single column of type t_customer appears as a column in the table structure.

4.2.2. Object Tables

An object table is a table in which each row contains one object of a given object type. Such objects are known as row objects. You create ...