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	<title>The Pythian Blog &#187; extended stats</title>
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		<title>Multi-Column Correlation and Extended Stats in Oracle 11g</title>
		<link>http://www.pythian.com/news/906/multi-column-correlation-and-extended-stats-in-oracle-11g/</link>
		<comments>http://www.pythian.com/news/906/multi-column-correlation-and-extended-stats-in-oracle-11g/#comments</comments>
		<pubDate>Wed, 09 Apr 2008 18:35:51 +0000</pubDate>
		<dc:creator>Riyaj Shamsudeen</dc:creator>
				<category><![CDATA[Group Blog Posts]]></category>
		<category><![CDATA[Oracle]]></category>
		<category><![CDATA[Oracle E-Business Suite]]></category>
		<category><![CDATA[11g]]></category>
		<category><![CDATA[cbo]]></category>
		<category><![CDATA[extended stats]]></category>
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		<guid isPermaLink="false">http://www.pythian.com/blogs/906/multi-column-correlation-and-extended-stats-in-oracle-11g</guid>
		<description><![CDATA[We all have encountered this situation many times before: the cost-based optimizer assumes no correlation between two columns (until 11g), and this has the effect of erroneously reducing the cardinality of a row source. Incorrect cardinality estimates are one of many root causes for SQL performance issues. Consider the following example. This code creates a [...]]]></description>
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