141 lines
7.6 KiB
HTML
141 lines
7.6 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Java user-defined table functions" />
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<meta name="abstract" content="DB2 provides the ability for a function to return a table. This is useful for exposing information from outside the database to the database in table form. For example, a table can be created that exposes the properties set in the Java virtual machine (JVM) used for Java stored procedures and Java UDFs (both table and scalar)." />
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<meta name="description" content="DB2 provides the ability for a function to return a table. This is useful for exposing information from outside the database to the database in table form. For example, a table can be created that exposes the properties set in the Java virtual machine (JVM) used for Java stored procedures and Java UDFs (both table and scalar)." />
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<meta name="DC.Relation" scheme="URI" content="writeudf.htm" />
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<meta name="DC.Relation" scheme="URI" content="udfrestr.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2006" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Java user-defined table functions</title>
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</head>
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<body id="udftable"><a name="udftable"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Java user-defined table functions</h1>
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<div><p>DB2<sup>®</sup> provides
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the ability for a function to return a table. This is useful for exposing
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information from outside the database to the database in table form. For example,
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a table can be created that exposes the properties set in the Java™ virtual
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machine (JVM) used for Java stored procedures and Java UDFs
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(both table and scalar).</p>
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<p>The <em>SQLJ Part 1: SQL Routines</em> standard does support table functions.
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Consequently, table functions are only available using parameter style DB2GENERAL.</p>
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<p>Five different types of calls are made to a table function. The following
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table explains these calls. These assume that scratchpad has been specified
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on the create function SQL statement.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" width="100%" frame="border" border="1" rules="all"><thead align="left"><tr><th align="left" valign="top" id="d0e39">Point in scan time</th>
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<th valign="top" id="d0e41">NO FINAL CALL LANGUAGE JAVA SCRATCHPAD</th>
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<th align="left" valign="top" id="d0e43">FINAL CALL LANGUAGE JAVA SCRATCHPAD</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e39 ">Before the first OPEN of the table function</td>
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<td valign="top" headers="d0e41 ">No calls</td>
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<td valign="top" headers="d0e43 ">Class constructor is called (means new scratchpad). UDF method is called
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with FIRST call. </td>
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</tr>
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<tr><td valign="top" headers="d0e39 ">At each OPEN of the table function.</td>
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<td valign="top" headers="d0e41 ">Class constructor is called (means new scratchpad). UDF method is called
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with OPEN all. </td>
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<td valign="top" headers="d0e43 ">UDF method is called with OPEN call. </td>
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</tr>
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<tr><td valign="top" headers="d0e39 ">At each FETCH for a new row of table function data. </td>
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<td valign="top" headers="d0e41 ">UDF method is called with FETCH call. </td>
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<td valign="top" headers="d0e43 ">UDF method is called with FETCH call. </td>
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</tr>
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<tr><td valign="top" headers="d0e39 ">At each CLOSE of the table function</td>
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<td valign="top" headers="d0e41 ">UDF method is called with CLOSE call. The close() method, if it exists,
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is also called.</td>
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<td valign="top" headers="d0e43 ">UDF method is called with CLOSE call.</td>
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</tr>
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<tr><td valign="top" headers="d0e39 ">After the last CLOSE of the table function. </td>
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<td valign="top" headers="d0e41 ">No calls</td>
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<td valign="top" headers="d0e43 ">UDF method is called with FINAL call. The close() method, if it exists,
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is also called.</td>
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</tr>
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</tbody>
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</table>
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</div>
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<div class="section"><h4 class="sectiontitle">Example: Java table function</h4><p>The following
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is an example of a Java table function that determines the
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properties set in the JVM used to run the Java user-defined table function.</p>
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<div class="note"><span class="notetitle">Note:</span> Read
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the <a href="codedisclaimer.htm">Code example disclaimer</a> for important
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legal information.</div>
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<pre> import com.ibm.db2.app.*;
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import java.util.*;
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public class JVMProperties extends UDF {
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Enumeration propertyNames;
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Properties properties ;
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public void dump (String property, String value) throws Exception
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{
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int callType = getCallType();
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switch(callType) {
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case SQLUDF_TF_FIRST:
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break;
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case SQLUDF_TF_OPEN:
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properties = System.getProperties();
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propertyNames = properties.propertyNames();
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break;
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case SQLUDF_TF_FETCH:
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if (propertyNames.hasMoreElements()) {
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property = (String) propertyNames.nextElement();
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value = properties.getProperty(property);
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set(1, property);
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set(2, value);
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} else {
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setSQLstate("02000");
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}
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break;
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case SQLUDF_TF_CLOSE:
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break;
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case SQLUDF_TF_FINAL:
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break;
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default:
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throw new Exception("UNEXPECT call type of "+callType);
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}
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}
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}</pre>
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<p>After the table function is compiled, and its class file
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copied to /QIBM/UserData/OS400/SQLLib/Function, the function can be registered
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to the database by using the following SQL statement.</p>
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<pre> create function properties()
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returns table (property varchar(500), value varchar(500))
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external name 'JVMProperties.dump' language java
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parameter style db2general fenced no sql
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disallow parallel scratchpad</pre>
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<p>After the function has been
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registered, it can be used as part of an SQL statement. For example, the following
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SELECT statement returns the table generated by the table function.</p>
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<pre> SELECT * FROM TABLE(PROPERTIES())</pre>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="writeudf.htm" title="A Java scalar function returns one value from a Java program to the database. For example, a scalar function could be created that returns the sum of two numbers.">Java user-defined scalar functions</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="udfrestr.htm" title="These restrictions apply to Java user-defined functions (UDFs).">Restrictions on Java user-defined functions</a></div>
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</div>
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</div>
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</body>
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</html>
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