149 lines
10 KiB
HTML
149 lines
10 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="Content-Type" content="text/html; charset=utf-8" />
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<meta name="DC.Title" content="Advanced data types" />
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<meta name="abstract" content="Advanced SQL3 data types give you a tremendous amount of flexibility. They are ideal for storing serialized Java objects, Extensible Markup Language (XML) documents, and multimedia data such as songs, product pictures, employee photographs, and movie clips. Java Database Connectivity (JDBC) 2.0 and higher provide support for working with these data types that are a part of the SQL99 standard." />
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<meta name="description" content="Advanced SQL3 data types give you a tremendous amount of flexibility. They are ideal for storing serialized Java objects, Extensible Markup Language (XML) documents, and multimedia data such as songs, product pictures, employee photographs, and movie clips. Java Database Connectivity (JDBC) 2.0 and higher provide support for working with these data types that are a part of the SQL99 standard." />
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<meta name="DC.Relation" scheme="URI" content="jdbc.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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<meta name="DC.Identifier" content="advancdt" />
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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>Advanced data types</title>
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</head>
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<body id="advancdt"><a name="advancdt"><!-- --></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">Advanced data types</h1>
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<div><p>Advanced SQL3 data types give you a tremendous amount of flexibility.
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They are ideal for storing serialized Java™ objects, Extensible Markup Language
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(XML) documents, and multimedia data such as songs, product pictures, employee
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photographs, and movie clips. Java Database Connectivity (JDBC) 2.0 and
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higher provide support for working with these data types that are a part of
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the SQL99 standard.</p>
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<div class="section"><h4 class="sectiontitle">Distinct types</h4><p>The distinct type is a user-defined
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type that is based on a standard database type. For example, you can define
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a Social Security Number type, SSN, that is a CHAR(9) internally. The following
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SQL statement creates such a DISTINCT type. </p>
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<blockquote><pre>CREATE DISTINCT TYPE CUJOSQL.SSN AS CHAR(9)</pre>
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</blockquote>
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<p>A
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distinct type always maps to a built-in data type. For more information on
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how and when to use distinct types in the context of SQL, consult the SQL
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reference manuals.</p>
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<p>To use distinct types in JDBC, you access them the
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same way that you access an underlying type. The getUDTs method is a new method
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that allows you to query what distinct types are available on the system. <a href="distinct.htm#distinct">Example: Distinct types</a> program shows the following:</p>
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<ul><li>The creation of a distinct type.</li>
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<li>The creation of a table that uses it.</li>
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<li>The use of a PreparedStatement to set a distinct type parameter.</li>
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<li>The use of a ResultSet to return a distinct type.</li>
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<li>The use of the metadata Application Programming Interface (API) call to
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getUDTs to learn about a distinct type.</li>
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</ul>
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<p>For more information, see the following example that shows various
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commons tasks you can perform by using distinct types:</p>
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<blockquote> <p><a href="distinct.htm#distinct">Example: Distinct types</a></p>
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</blockquote>
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</div>
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<div class="section"><h4 class="sectiontitle">Large Objects</h4><p> There are three types of Large Objects
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(LOBs): </p>
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<ul><li>Binary Large Objects (BLOBs)</li>
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<li>Character Large Objects (CLOBs)</li>
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<li>Double Byte Character Large Objects (DBCLOBs)</li>
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</ul>
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<p> DBCLOBs are similar to CLOBs except for their internal storage representation
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of the character data. Because Java and JDBC externalize all character
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data as Unicode, there is only support in JDBC for CLOBs. DBCLOBs work interchangeable
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with the CLOB support from a JDBC perspective. </p>
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</div>
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<div class="section"><h4 class="sectiontitle">Binary Large Objects</h4><p>In many ways, a Binary Large
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Object (BLOB) column is similar to a CHAR FOR BIT DATA column that can be
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made large. You can store anything in these columns that can be represented
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as a stream of nontranslated bytes. Often, BLOB columns are used to store
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serialized Java objects, pictures, songs, and other binary data.</p>
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<p>You
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can use BLOBs the same way you can use other standard database
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types. You can pass them to stored procedures, use them in prepared statements,
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and update them in result sets. The PreparedStatement class has a setBlob
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method for passing BLOBs to the database, and the ResultSet class adds a getBlob
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class for retrieving them from the database. A BLOB is represented in a Java program
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by a BLOB object that is a JDBC interface.</p>
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<p>Refer to <a href="adwrblob.htm">Write
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code that uses BLOBs</a> for more information about how to use BLOBs.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Character Large Objects</h4><p>Character Large Objects
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(CLOBs) are the character data complement to BLOBs. Instead of storing data
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in the database without translation, the data is stored in the database as
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text and is processed the same way as a CHAR column. As with BLOBs, JDBC 2.0
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provides functions for dealing directly with CLOBs. The PreparedStatement
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interface contains a setClob method and the ResultSet interface contains a
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getClob method.</p>
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<p>Refer to <a href="adwrclob.htm">Write code that
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uses CLOBs</a> for more information about how to use CLOBs.</p>
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<p>Although
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BLOB and CLOB columns work like CHAR FOR BIT DATA and CHAR columns, this is
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conceptually how they work from an external user's perspective. Internally,
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they are different; because of the potentially enormous size of Large Object
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(LOB) columns, you typically work indirectly with data. For example, when
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a block of rows is fetched from the database, you do not move a block of LOBs
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to the ResultSet. You move pointers called LOB locators (that is, four-byte
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integers) into the ResultSet instead. However, it is not necessary to know
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about locators when working with LOBs in JDBC.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Datalinks</h4><p><strong>Datalinks</strong> are encapsulated values
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that contain a logical reference from the database to a file stored outside
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the database. Datalinks are represented and used from a JDBC perspective in
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two different ways, depending on whether you are using JDBC 2.0 or earlier,
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or you are using JDBC 3.0 or later.</p>
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<p>Refer to <a href="adwrdlnk.htm">Write
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code that uses Datalinks</a> for more information about how to use Datalinks.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Unsupported SQL3 data types</h4><p>There are other SQL3
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data types that have been defined and for which the JDBC API provides support.
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These are ARRAY, REF, and STRUCT. Presently, iSeries™ servers do not support these
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types. Therefore, the JDBC driver does not provide any form of support for
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them.</p>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="adwrblob.htm">Write code that uses BLOBs</a></strong><br />
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There are a number of tasks that can be accomplished with database
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Binary Large Object (BLOB) columns through the Java Database Connectivity (JDBC) Application
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Programming Interface (API). The following topics briefly discuss these tasks
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and include examples on how to accomplish them.</li>
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<li class="ulchildlink"><strong><a href="adwrclob.htm">Write code that uses CLOBs</a></strong><br />
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There are a number of tasks that can be performed with database
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CLOB and DBCLOB columns through the Java Database Connectivity (JDBC) Application
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Programming Interface (API). The following topics briefly discuss these tasks
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and include examples on how to accomplish them.</li>
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<li class="ulchildlink"><strong><a href="adwrdlnk.htm">Write code that uses Datalinks</a></strong><br />
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How you work with Datalinks is dependent on what release you are working with. In JDBC 3.0, there is support to work directly with Datalink columns using the getURL and putURL methods.</li>
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<li class="ulchildlink"><strong><a href="distinct.htm">Example: Distinct types</a></strong><br />
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This is an example of how to use distinct types.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="jdbc.htm" title="The IBM Developer Kit for Java JDBC driver, also known as the "native" driver, provides programmatic access to iSeries database files. Using the Java Database Connectivity (JDBC) API, applications written in the Java language can access JDBC database functions with embedded Structured Query Language (SQL), run SQL statements, retrieve results, and propagate changes back to the database. The JDBC API can also be used to interact with multiple data sources in a distributed, heterogeneous environment.">Access your iSeries database with the IBM Developer Kit for Java JDBC driver</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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