112 lines
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112 lines
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<title>Describe database files</title>
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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">Describe database files</h1>
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<div><p>These topics introduce several methods for describing <span class="keyword">iSeries™</span> database files, with focus on
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how to describe database files using data description specifications (DDS)
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because DDS has the most options for defining data. </p>
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<p></p>
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<p>If you want to describe a file just to the record level, you can use the
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record length (RCDLEN) parameter on the Create Physical File (CRTPF) and Create
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Source Physical File (CRTSRCPF) commands. If you want to describe your file
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to the field level, several methods can be used to describe data to the database
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system: interactive data definition utility (IDDU), Structured Query Language
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(SQL) commands, or data description specifications (DDS).</p>
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<div class="p"> <dl><dt class="dlterm">Interactive data definition utility (IDDU)</dt>
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<dd> <p>Physical files can be described using IDDU.
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You might use IDDU because it is a menu-driven, interactive method of describing
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data. You might be familiar with describing data using IDDU on a System/36™.
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In addition, IDDU allows you to describe multiple-format physical files for
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use with Query, iSeries Access,
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and data file utility (DFU).</p>
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<p>When you use IDDU to describe your files,
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the file definition becomes part of the i5/OS™ data dictionary.</p>
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</dd>
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<dt class="dlterm"><span class="keyword">DB2 Universal Database™ for iSeries</span> Structured
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Query Language (SQL)</dt>
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<dd> <p>SQL can be used
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to describe an <span class="keyword">iSeries</span> database
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file. It supports statements to describe the fields in the database file,
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and to create the file.</p>
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<p>SQL was created by IBM<sup>®</sup> to meet the need for a standard and
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common database language. It is currently used on all IBM DB2 platforms and on many other database
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implementations from many different manufacturers.</p>
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<p>When database files
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are created using the <span class="keyword">DB2 UDB for iSeries</span> SQL
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language, the description of the file is automatically added to a data dictionary
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in the SQL collection. The data dictionary (or catalog) is then automatically
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maintained by the system.</p>
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<p>SQL is the language of choice for accessing
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databases on many other platforms. It is the only language for distributed
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database and heterogeneous systems.</p>
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</dd>
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<dt class="dlterm">Data description specifications (DDS)</dt>
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<dd> <p>Externally
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described data files can be described using DDS. Using DDS, you provide descriptions
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of the field, record, and file level information.</p>
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<p>You might use DDS
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because it provides the most options for the programmer to describe data in
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the database. For example, only with DDS can you describe key fields in logical
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files.</p>
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<p>The DDS form provides a common format for describing data externally.
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DDS data is column sensitive. The examples in this manual have numbered columns
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and show the data in the correct columns.</p>
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</dd>
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</dl>
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</div>
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<p>After a database file is described, you can view the description.</p>
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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="rbafodescdds.htm">Describe database files using DDS</a></strong><br />
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When you describe a database file using data description specifications (DDS), you can describe information at the file, record-format, join, field, key, and select/omit levels.</li>
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<li class="ulchildlink"><strong><a href="rbafocrtatt.htm">Specify database file and member attributes</a></strong><br />
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When you create a database file, database attributes are stored with the file and members. You specify attributes with database command parameters.</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="rbafocrtdbf.htm" title="This topic provides an overview of the process of creating database files, libraries, source files, and physical files.">Create and describe database files</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="../books/sc415704.pdf" target="_blank">IDDU Use PDF</a></div>
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<div><a href="../sqlp/rbafykickoff.htm">SQL programming</a></div>
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<div><a href="../db2/rbafzmst02.htm">DB2 UDB for iSeries SQL Reference</a></div>
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<div><a href="rbafofilexr.htm" title="You can display the file attributes for database files and device files using the display table description operation in iSeries Navigator.">Display information about database files</a></div>
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</div>
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</div>
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</body>
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