Symbian3/PDK/Source/GUID-12CB6E0E-69CD-51A6-8966-3621CB26E1CD.dita
author Dominic Pinkman <Dominic.Pinkman@Nokia.com>
Fri, 22 Jan 2010 18:26:19 +0000
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Addition of the PDK content and example code for Documentation_content according to Feature bug 1607 and bug 1608
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<?xml version="1.0" encoding="utf-8"?>
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<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
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<!-- This component and the accompanying materials are made available under the terms of the License 
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"Eclipse Public License v1.0" which accompanies this distribution, 
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and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
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<!-- Initial Contributors:
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    Nokia Corporation - initial contribution.
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Contributors: 
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-->
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<!DOCTYPE concept
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  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
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<concept xml:lang="en" id="GUID-12CB6E0E-69CD-51A6-8966-3621CB26E1CD"><title>DBMS rowsets overview</title><prolog><metadata><keywords/></metadata></prolog><conbody><section><title>Purpose</title> <p>Allows data contained in a database to be retrieved, searched, and modified.</p> </section> <section><title>Description</title> <p>The API has three key concepts: rowset base, table rowset, and SQL view. </p> <p><b>Rowset base</b> </p> <p>Rowsets provide the following:</p> <ul><li id="GUID-5EC6A9C9-2C0F-5141-A600-815C61FA5DC8"><p>retrieving data from a database</p> </li> <li id="GUID-145F724B-4AFF-5987-9DC1-C94D5FE9C54C"><p>navigating the rowset with a cursor</p> </li> <li id="GUID-BD487F4B-D14F-5575-95BB-2A1A5ECBC020"><p>row finding and matching </p> </li> <li id="GUID-56F7E17F-3009-5E2C-A015-CF09D03C98F1"><p>updating or inserting rows</p> </li> <li id="GUID-FE9D6B32-74CE-54C7-8DBB-C7578673282F"><p>getting the schema of the rows within the rowset</p> </li> <li id="GUID-FA52E8CD-8943-560F-8613-BF7D0E6A05A8"><p>extracting and setting columns in a row</p> </li> </ul> <p>A base class is defined for all rowset types by <xref href="GUID-F861EB8F-F621-3E77-8F9A-5E4EFC4E9C2F.dita"><apiname>RDbRowSet</apiname></xref>. Concrete types of rowset derive from this.</p> <p><b>Table rowset</b> </p> <p>This provides all the rows and columns of a table as a rowset. Indexes can be used to order the rowset, and to provide fast key-based row retrieval from the table. It is encapsulated in <xref href="GUID-90ABFA73-6374-367C-BAA9-88CD810035CC.dita"><apiname>RDbTable</apiname></xref>. </p> <p><b>SQL view</b> </p> <p>This provides a rowset based on an SQL query. It is provided by <xref href="GUID-AE1BEF00-5AA7-3F03-95B0-9E40395EDA6C.dita"><apiname>RDbView</apiname></xref>. An SQL query is encapsulated in <xref href="GUID-A7C9FEFA-A9A9-357F-AF66-FA3A288AF925.dita"><apiname>TDbQuery</apiname></xref>.</p> <p>For large rowsets, it can be useful to define the balance between memory usage (greatest if the view stores the complete rowset) and speed (slowest if the rowset is evaluated for each cursor navigation). This is called the pre-evaluation window, and is provided by <xref href="GUID-E53A90DF-3589-34BD-B7C3-02371567AF41.dita"><apiname>TDbWindow</apiname></xref>.</p> </section> </conbody></concept>