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Java > Open Source Codes > com > quadcap > sql > JoinUnionCursor


1 package com.quadcap.sql;
2
3 /* Copyright 1999 - 2003 Quadcap Software. All rights reserved.
4  *
5  * This software is distributed under the Quadcap Free Software License.
6  * This software may be used or modified for any purpose, personal or
7  * commercial. Open Source redistributions are permitted. Commercial
8  * redistribution of larger works derived from, or works which bundle
9  * this software requires a "Commercial Redistribution License"; see
10  * http://www.quadcap.com/purchase.
11  *
12  * Redistributions qualify as "Open Source" under one of the following terms:
13  *
14  * Redistributions are made at no charge beyond the reasonable cost of
15  * materials and delivery.
16  *
17  * Redistributions are accompanied by a copy of the Source Code or by an
18  * irrevocable offer to provide a copy of the Source Code for up to three
19  * years at the cost of materials and delivery. Such redistributions
20  * must allow further use, modification, and redistribution of the Source
21  * Code under substantially the same terms as this license.
22  *
23  * Redistributions of source code must retain the copyright notices as they
24  * appear in each source code file, these license terms, and the
25  * disclaimer/limitation of liability set forth as paragraph 6 below.
26  *
27  * Redistributions in binary form must reproduce this Copyright Notice,
28  * these license terms, and the disclaimer/limitation of liability set
29  * forth as paragraph 6 below, in the documentation and/or other materials
30  * provided with the distribution.
31  *
32  * The Software is provided on an "AS IS" basis. No warranty is
33  * provided that the Software is free of defects, or fit for a
34  * particular purpose.
35  *
36  * Limitation of Liability. Quadcap Software shall not be liable
37  * for any damages suffered by the Licensee or any third party resulting
38  * from use of the Software.
39  */
40
41 import java.io.IOException JavaDoc;
42
43 import java.sql.SQLException JavaDoc;
44
45
46 /**
47  * Half of a <b>UNION</b> join. Can be used to synthesize <b>UNION</b> and
48  * <b>FULL</b> joins.
49  *
50  * @author Stan Bailes
51  */
52 public class JoinUnionCursor extends JoinCursor {
53     boolean beforeSecond = true;
54     
55     public JoinUnionCursor(Session session, Cursor outer, Cursor ca, Cursor cb,
56                            Expression where, Tuple tuple, JoinMapRow row)
57     throws SQLException JavaDoc
58     {
59         super(session, outer, ca, cb, where, tuple, row, false, false);
60     }
61                                
62     public boolean next() throws SQLException JavaDoc {
63     boolean ret = false;
64         if (beforeSecond) {
65             ret = anext();
66             if (!ret) {
67                 beforeSecond = false;
68                 ret = bnext();
69             }
70         } else {
71             ret = bnext();
72         }
73         return ret;
74     }
75 }
76
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