266 lines
15 KiB
HTML
266 lines
15 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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<!-- Use, duplication or disclosure restricted by -->
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<meta name="dc.date" scheme="iso8601" content="2005-09-19" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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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="keywords" content="CREATE INDEX statement, CREATE INDEX,
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SQL statements, INDEX clause, UNIQUE clause, in CREATE INDEX statement,
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WHERE NOT NULL clause, ENCODED VECTOR clause, index-name, ON clause, table-name,
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ASC clause, DESC clause, WITH DISTINCT VALUES clause, PARTITIONED clause,
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NOT PARTITIONED clause, PAGESIZE clause" />
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<title>CREATE INDEX</title>
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<link rel="stylesheet" type="text/css" href="ibmidwb.css" />
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<link rel="stylesheet" type="text/css" href="ic.css" />
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</head>
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<body>
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<a id="Top_Of_Page" name="Top_Of_Page"></a><!-- Java sync-link -->
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<script language = "Javascript" src = "../rzahg/synch.js" type="text/javascript"></script>
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<a name="xcindx"></a>
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<h2 id="xcindx"><a href="rbafzmst02.htm#ToC_888">CREATE INDEX</a></h2><a id="idx1896" name="idx1896"></a><a id="idx1897" name="idx1897"></a><a id="idx1898" name="idx1898"></a>
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<a name="cindx"></a>
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<p id="cindx">The CREATE INDEX statement creates an index on a table at the
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current server.</p>
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<a name="wq1249"></a>
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<h3 id="wq1249"><a href="rbafzmst02.htm#ToC_889">Invocation</a></h3>
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<p>This statement can be embedded in an application program or issued interactively.
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It is an executable statement that can be dynamically prepared.</p>
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<a name="wq1250"></a>
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<h3 id="wq1250"><a href="rbafzmst02.htm#ToC_890">Authorization</a></h3>
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<p>The privileges held by the authorization ID of the statement must include
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at least one of the following:</p>
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<ul>
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<li>The privilege to create in the schema. For more information, see <a href="rbafzmstauthown.htm#createin">Privileges necessary to create in a schema</a>.</li>
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<li>Administrative authority</li></ul>
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<p>The privileges held by the authorization ID of the statement must include
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at least one of the following: </p>
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<ul>
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<li>The following system authorities:
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<ul>
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<li>*USE to the Create Logical File (CRTLF) command</li>
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<li>*CHANGE to the data dictionary if the library into which the index is
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created is an SQL schema with a data dictionary</li></ul></li>
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<li>Administrative authority</li></ul>
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<p>The privileges held by the authorization ID of the statement must also
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include at least one of the following: </p>
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<ul>
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<li>For the referenced table:
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<ul>
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<li>The INDEX privilege on the table</li>
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<li>The system authority *EXECUTE on the library containing the table</li></ul></li>
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<li>Administrative authority</li></ul>
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<p>If SQL names are specified and a user profile exists that has the same
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name as the library into which the table is created, and that name is different
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from the authorization ID of the statement, then the privileges held by the
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authorization ID of the statement must include at least one of the following: </p>
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<ul>
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<li>The system authority *ADD to the user profile with that name</li>
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<li>Administrative authority</li></ul>
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<p>For information on the system authorities corresponding to SQL privileges,
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see <a href="rbafzmstgnt.htm#eqtablet">Corresponding System Authorities When Checking Privileges to a Table or View</a>.</p>
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<a name="wq1251"></a>
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<h3 id="wq1251"><a href="rbafzmst02.htm#ToC_891">Syntax</a></h3>
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<a href="rbafzmstxcindx.htm#synscrtidx"><img src="c.gif" alt="Click to skip syntax diagram" /></a>
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<pre class="cgraphic"><span><img src="c.gif" alt="Read syntax diagram" longdesc="rbafzmstsyn290.htm"
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border="0" /></span><a href="#skipsyn-289"><img src="c.gif" alt="Skip visual syntax diagram"
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border="0" /></a>>>-CREATE--+----------------------------+--INDEX--<span class="italic">index-name</span>---->
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+-UNIQUE--+----------------+-+
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| '-WHERE NOT NULL-' |
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'-ENCODED VECTOR-------------'
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.-,---------------------.
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V .-ASC--. |
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>--ON--<span class="italic">table-name</span>--(----<span class="italic">column-name</span>--+------+-+--)-------------->
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'-DESC-'
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>--<span class="italic">index-options</span>-----------------------------------------------><
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index-options:
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|--+-------------------------------------+---------------------->
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| .-DISTINCT-. |
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'-WITH--<span class="italic">integer</span>--+----------+--VALUES-'
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.-<span>PAGESIZE</span>--<span><span class="italic">64</span></span>------. (1)
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>--+-----------------+--+-------------------+-------------------|
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+-NOT PARTITIONED-+ '-<span>PAGESIZE</span>--+-<span>8</span>---+-'
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'-PARTITIONED-----' +-<span>16</span>--+
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+-<span>32</span>--+
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+-<span>64</span>--+
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+-<span>128</span>-+
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'-<span>512</span>-'
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</pre>
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<a name="skipsyn-289" id="skipsyn-289"></a>
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<a name="wq1252"></a>
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<div class="notelisttitle" id="wq1252">Notes:</div>
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<ol type="1">
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<li>The <var class="pv">index-options</var> may be specified in any order.</li>
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</ol>
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<a name="synscrtidx"></a>
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<h3 id="synscrtidx"><a href="rbafzmst02.htm#ToC_892">Description</a></h3>
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<dl class="parml">
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<dt class="bold">UNIQUE </dt><a id="idx1899" name="idx1899"></a>
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<dd>Prevents the table from containing two or more rows with the same value
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of the index key. The constraint is enforced when rows of the table are updated
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or new rows are inserted.
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<p>The constraint is also checked during the execution
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of the CREATE INDEX statement. If the table already contains rows with duplicate
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key values, the index is not created.</p>
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<p>When UNIQUE is used, null values
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are treated as any other values. For example, if the key is a single column
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that can contain null values, that column can contain no more than one null
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value.</p>
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</dd>
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<dt class="bold">UNIQUE WHERE NOT NULL</dt><a id="idx1900" name="idx1900"></a><a id="idx1901" name="idx1901"></a>
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<dd>Prevents the table from containing two or more rows with the same nonnull
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value of the index key. Multiple null values are allowed; otherwise, this
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is identical to UNIQUE.
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</dd>
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<dt class="bold">ENCODED VECTOR </dt><a id="idx1902" name="idx1902"></a>
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<dd>Specifies that the resulting index will be an encoded vector index (EVI).
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<p>An encoded vector index cannot be used to ensure an ordering of rows. It is
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used by the database manager to improve the performance of queries. For more
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information, see the <a href="../rzajq/rzajqkickoff.htm">Database Performance and Query Optimization</a> book.</p>
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</dd>
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<dt class="bold"><var class="pv">index-name</var> </dt><a id="idx1903" name="idx1903"></a>
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<dd>Names the index. The name, including the implicit or explicit qualifier,
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must not be the same as an index, table, view, alias, or file that already
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exists at the current server.
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<p>If SQL names were specified, the index will
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be created in the schema specified by the implicit or explicit qualifier.</p>
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<p>If system names were specified, the index name will be created in the
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schema that is specified by the qualifier. If not qualified, the index name
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will be created in the same schema as the table over which the index is created.</p>
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<p>If the index name is not a valid system name, DB2 UDB for iSeries will generate a
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system name. For information on the rules for generating a name, see <a href="rbafzmsthctabl.htm#namrul">Rules for Table Name Generation</a>.</p>
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</dd>
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<dt class="bold">ON <var class="pv">table-name</var> </dt><a id="idx1904" name="idx1904"></a><a id="idx1905" name="idx1905"></a>
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<dd>Identifies the table on which the index is to be created. The <var class="pv">table-name</var> must identify a base table (not a view) that exists at the current server.
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<p>If the table is a partitioned table, an alias may be specified which identifies
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a single partition. The created index will then only be created over the specified
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partition.</p>
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</dd>
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<dt class="bold"><var class="pv">(column-name, ... )</var></dt>
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<dd>Identifies the list of columns that will be part of the index
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key.
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<p>Each <var class="pv">column-name</var> must be an unqualified name that identifies
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a column of the table. The same column may be specified more than once. A <var class="pv">column-name</var> must not identify a LOB or DATALINK column, or a distinct
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type based on a LOB or DATALINK column. The number of columns must not exceed
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120, and the sum of their byte lengths must not exceed 32766-<span class="italic">n</span>, where <span class="italic">n</span> is the number of columns specified
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that allows nulls. </p>
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<dl class="parml">
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<dt class="bold">ASC </dt><a id="idx1906" name="idx1906"></a>
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<dd>Specifies that the index entries are to be kept in ascending
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order of the column values. ASC is the default.
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</dd>
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<dt class="bold">DESC </dt><a id="idx1907" name="idx1907"></a>
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<dd>Specifies that the index entries are to be kept in descending order
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of the column values.
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</dd>
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</dl>
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</dd>
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<dt class="bold">WITH <var class="pv">integer</var> DISTINCT VALUES </dt><a id="idx1908" name="idx1908"></a>
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<dd>Specifies the estimated number of distinct key values. This clause may
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be specified for any type of index.
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<p>For encoded vector indexes this is
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used to determine the initial size of the codes assigned to each distinct
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key value. The default value is 256.</p>
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<p>For non-encoded vector indexes,
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this is used as a hint to the optimizer.</p>
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</dd>
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<dt class="bold">PARTITIONED</dt><a id="idx1909" name="idx1909"></a>
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<dd>Specifies that an index partition should be created for each data partition
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defined for the table using the specified columns. The <var class="pv">table-name</var> must
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identify a partitioned table. If the index is unique, the columns of the index
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must be the same or a superset of the columns of the data partition key. PARTITIONED
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is the default if the index is not unique and the table is partitioned.
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</dd>
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<dt class="bold">NOT PARTITIONED</dt><a id="idx1910" name="idx1910"></a>
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<dd>Specifies that a single index should be created that spans all of the
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data partitions defined for the table. The <var class="pv">table-name</var> must identify
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a partitioned table. NOT PARTITIONED is the default if the index is unique
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and the table is partitioned. An index on a table that is not partitioned
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is also by default not partitioned.
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<p>If an encoded vector index is specified,
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NOT PARTITIONED is not allowed.</p>
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</dd>
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<dt class="bold">PAGESIZE</dt><a id="idx1911" name="idx1911"></a>
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<dd>Specifies the logical page used for the index in kilobytes. Indexes
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with larger logical page sizes are typically more efficient when scanned during
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query processing. Indexes with smaller logical page sizes are typically more
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efficient for simple index probes and individual key look ups.
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<p>The default value for PAGESIZE is determined by the length of the key and
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with a minimum value of 64.</p>
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<p>If an encoded vector index is specified,
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PAGESIZE is not allowed.</p>
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</dd>
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</dl>
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<a name="wq1254"></a>
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<h3 id="wq1254"><a href="rbafzmst02.htm#ToC_893">Notes</a></h3>
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<p><span class="bold">Effects of the statement:</span> CREATE INDEX creates a
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description of the index. If the named table already contains data, CREATE
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INDEX creates the index entries for it. If the table does not yet contain
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data, the index entries are created when data is inserted into the table.</p>
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<p><span class="bold">Sort sequence:</span> Any index created over columns containing
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SBCS or mixed data is created with the sort sequence in effect at the time
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the statement is executed. For sort sequences other than *HEX, the key for
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SBCS data or mixed data is the weighted value of the key based on the sort
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sequence.</p>
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<p><span class="bold">Index attributes:</span> An index is created as a keyed
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logical file. When an index is created, the file wait time and record wait
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time attributes are set to the default that is specified on the WAITFILE and
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WAITRCD keywords of the Create Logical File (CRTLF) command.</p>
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<p>An index created over a distributed table is created on all of the servers
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across which the table is distributed. For more information about distributed
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tables, see the <a href="../dbmult/rzaf3kickoff.htm">DB2® Multisystem</a> book.</p>
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<p><span class="bold">Index ownership:</span> If SQL names were specified:</p>
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<ul>
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<li>If a user profile with the same name as the schema into which the index
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is created exists, the <span class="italic">owner</span> of the index is that
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user profile.</li>
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<li>Otherwise, the <span class="italic">owner</span> of the index is the user
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profile or group user profile of the job executing the statement.</li></ul>
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<p>If system names were specified, the <span class="italic">owner</span> of the
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index is the user profile or group user profile of the job executing the statement.</p>
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<p><span class="bold">Index authority:</span> If SQL names are used, indexes are
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created with the system authority of *EXCLUDE on *PUBLIC. If system names
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are used, indexes are created with the authority to *PUBLIC as determined
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by the create authority (CRTAUT) parameter of the schema.</p>
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<p>If the owner of the index is a member of a group profile (GRPPRF keyword)
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and group authority is specified (GRPAUT keyword), that group profile will
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also have authority to the index.</p>
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<a name="wq1255"></a>
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<h3 id="wq1255"><a href="rbafzmst02.htm#ToC_894">Examples</a></h3>
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<p><span class="italic">Example 1:</span> Create an index named UNIQUE_NAM
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on the PROJECT table. The purpose of the index is to ensure that there are
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not two entries in the table with the same value for project name (PROJNAME).
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The index entries are to be in ascending order.</p>
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<p> </p>
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<pre class="xmp"> <span class="bold">CREATE UNIQUE INDEX</span> UNIQUE_NAM
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<span class="bold">ON</span> PROJECT<span class="bold">(</span>PROJNAME<span class="bold">)</span></pre>
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<p><span class="italic">Example 2:</span> Create an index named JOB_BY_DPT
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on the EMPLOYEE table. Arrange the index entries in ascending order by job
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title (JOB) within each department (WORKDEPT). </p>
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<pre class="xmp"> <span class="bold">CREATE INDEX</span> JOB_BY_DPT
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<span class="bold">ON</span> EMPLOYEE <span class="bold">(</span>WORKDEPT, JOB<span class="bold">)</span></pre>
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<hr /><br />
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[ <a href="#Top_Of_Page">Top of Page</a> | <a href="rbafzmstcftb.htm">Previous Page</a> | <a href="rbafzmstcreatep.htm">Next Page</a> | <a href="rbafzmst02.htm#wq1">Contents</a> |
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<a href="rbafzmstindex.htm#index">Index</a> ]
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<a id="Bot_Of_Page" name="Bot_Of_Page"></a>
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</body>
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</html>
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