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<h2 class="title"><a id="DB"></a>Chapter 7. Databases</h2>
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<div class="toc">
<p>
<b>Table of Contents</b>
</p>
<dl>
<dt>
<span class="sect1">
<a href="DB.html#DBOpen">Opening Databases</a>
</span>
</dt>
<dt>
<span class="sect1">
<a href="coredbclose.html">Closing Databases</a>
</span>
</dt>
<dt>
<span class="sect1">
<a href="DBConfig.html">Database Properties</a>
</span>
</dt>
<dt>
<span class="sect1">
<a href="DBAdmin.html">Administrative Methods</a>
</span>
</dt>
<dt>
<span class="sect1">
<a href="dbErrorReporting.html">Error Reporting Functions</a>
</span>
</dt>
<dt>
<span class="sect1">
<a href="CoreEnvUsage.html">Managing Databases in Environments</a>
</span>
</dt>
<dt>
<span class="sect1">
<a href="CoreJavaUsage.html">Database Example</a>
</span>
</dt>
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<p>In Berkeley DB, a database is a collection of <span class="emphasis"><em>records</em></span>. Records,
in turn, consist of key/data pairings.
</p>
<p>
Conceptually, you can think of a
<tt class="classname">Database</tt>
as containing a two-column table where column 1 contains a key and column 2
contains data. Both the key and the data are managed using
<tt class="classname">DatabaseEntry</tt>
<span>class instances</span>
(see <a href="DBEntry.html">Database Records</a> for details on this
<span>class</span>
).
So, fundamentally, using a DB
<tt class="classname">Database</tt>
involves putting, getting, and deleting database records, which in turns involves efficiently
managing information
<span>encapsulated by </span>
<tt class="classname">DatabaseEntry</tt>
<span>objects.</span>
The next several chapters of this book are dedicated to those activities.
</p>
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<div>
<h2 class="title" style="clear: both"><a id="DBOpen"></a>Opening Databases</h2>
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<div></div>
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<p>
You open a database by instantiating a <tt class="classname">Database</tt>
object.
</p>
<p>
Note that by default, DB does not create databases if they do not already exist.
To override this behavior, set the <a href="DBConfig.html" title="Database Properties">creation property</a> to true.
</p>
<p>
The following code fragment illustrates a database open:
</p>
<a id="java_db1"></a>
<pre class="programlisting">package db.GettingStarted;
import com.sleepycat.db.DatabaseException;
import com.sleepycat.db.Database;
import com.sleepycat.db.DatabaseConfig;
import java.io.FileNotFoundException;
...
Database myDatabase = null;
...
try {
// Open the database. Create it if it does not already exist.
DatabaseConfig dbConfig = new DatabaseConfig();
dbConfig.setAllowCreate(true);
myDatabase = new Database ("sampleDatabase.db",
null,
dbConfig);
} catch (DatabaseException dbe) {
// Exception handling goes here
} catch (FileNotFoundException fnfe) {
// Exception handling goes here
}</pre>
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