/*
 * @(#)Joinable.java	1.6 05/11/17
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package javax.sql.rowset;

import java.sql.SQLException;

/**
 * <h3>1.0 Background</h3>
 * The <code>Joinable</code> interface provides the methods for getting and
 * setting a match column, which is the basis for forming the SQL <code>JOIN</code>
 * formed by adding <code>RowSet</code> objects to a <code>JoinRowSet</code>
 * object.
 * <P>
 * Any standard <code>RowSet</code> implementation <b>may</b> implement 
 * the <code>Joinable</code> interface in order to be
 * added to a <code>JoinRowSet</code> object. Implementing this interface gives
 * a <code>RowSet</code> object the ability to use <code>Joinable</code> methods,
 * which set, retrieve, and get information about match columns.  An
 * application may add a
 * <code>RowSet</code> object that has not implemented the <code>Joinable</code>
 * interface to a <code>JoinRowSet</code> object, but to do so it must use one
 * of the <code>JoinRowSet.addRowSet</code> methods that takes both a
 * <code>RowSet</code> object and a match column or an array of <code>RowSet</code>
 * objects and an array of match columns. 
 * <P>
 * To get access to the methods in the <code>Joinable</code> interface, a
 * <code>RowSet</code> object implements at least one of the
 * five standard <code>RowSet</code> interfaces and also implements the 
 * <code>Joinable</code> interface.  In addition, most <code>RowSet</code>
 * objects extend the <code>BaseRowSet</code> class.  For example:
 * <pre>
 *     class MyRowSetImpl extends BaseRowSet implements CachedRowSet, Joinable {
 *         :
 *         :
 *     }
 * </pre>
 * <P>
 * <h3>2.0 Usage Guidelines</h3>
 * <P>
 * The methods in the <code>Joinable</code> interface allow a <code>RowSet</code> object 
 * to set a match column, retrieve a match column, or unset a match column, which is
 * the column upon which an SQL <code>JOIN</code> can be based.
 * An instance of a class that implements these methods can be added to a 
 * <code>JoinRowSet</code> object to allow an SQL <code>JOIN</code> relationship to
 *  be established.
 * <p>
 * <pre>
 *     CachedRowSet crs = new MyRowSetImpl();
 *     crs.populate((ResultSet)rs);
 *     (Joinable)crs.setMatchColumnIndex(1);
 *
 *     JoinRowSet jrs = new JoinRowSetImpl();
 *     jrs.addRowSet(crs);
 * </pre>
 * In the previous example, <i>crs</i> is a <code>CachedRowSet</code> object that
 * has emplemented the <code>Joinable</code> interface.  In the following example,
 * <i>crs2</i> has not, so it must supply the match column as an argument to the
 * <code>addRowSet</code> method. This example assumes that column 1 is the match
 * column.
 * <PRE>
 *     CachedRowSet crs2 = new MyRowSetImpl();
 *     crs2.populate((ResultSet)rs);
 *     
 *     JoinRowSet jrs2 = new JoinRowSetImpl();
 *     jrs2.addRowSet(crs2, 1);
 * </PRE>
 * <p>
 * The <code>JoinRowSet</code> interface makes it possible to get data from one or
 * more <code>RowSet</code> objects consolidated into one table without having to incur 
 * the expense of creating a connection to a database. It is therefore ideally suited
 * for use by disconnected <code>RowSet</code> objects. Nevertheless, any
 * <code>RowSet</code> object <b>may</b> implement this interface
 * regardless of whether it is connected or disconnected. Note that a
 * <code>JdbcRowSet</code> object, being always connected to its data source, can
 * become part of an SQL <code>JOIN</code> directly without having to become part
 * of a <code>JoinRowSet</code> object. 
 * <P>
 * <h3>3.0 Managing Multiple Match Columns</h3>
 * The index array passed into the <code>setMatchColumn</code> methods indicates 
 * how many match columns are being set (the length of the array) in addition to
 * which columns will be used for the match. For example:
 * <pre>
 *     int[] i = {1, 2, 4, 7}; // indicates four match columns, with column
 *                             // indexes 1, 2, 4, 7 participating in the JOIN.
 *     Joinable.setMatchColumn(i);
 * </pre>
 * Subsequent match columns may be added as follows to a different <code>Joinable</code>
 * object (a <code>RowSet</code> object that has implemented the <code>Joinable</code>
 * interface).
 * <pre>
 *     int[] w = {3, 2, 5, 3};
 *     Joinable2.setMatchColumn(w);
 * </pre>
 * When an application adds two or more <code>RowSet</code> objects to a
 * <code>JoinRowSet</code> object, the order of the indexes in the array is