<?xml version="1.0" encoding="UTF-8"?><rss version="2.0"
	xmlns:media="http://search.yahoo.com/mrss/"
	xmlns:content="http://purl.org/rss/1.0/modules/content/"
	xmlns:wfw="http://wellformedweb.org/CommentAPI/"
	xmlns:dc="http://purl.org/dc/elements/1.1/"
	xmlns:atom="http://www.w3.org/2005/Atom"
	xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
	xmlns:slash="http://purl.org/rss/1.0/modules/slash/"
	>

<channel>
	<title>去重 - 四号程序员</title>
	<atom:link href="https://www.coder4.com/archives/tag/%E5%8E%BB%E9%87%8D/feed" rel="self" type="application/rss+xml" />
	<link>https://www.coder4.com</link>
	<description>Keep It Simple and Stupid</description>
	<lastBuildDate>Wed, 03 Jun 2020 22:18:15 +0000</lastBuildDate>
	<language>en-US</language>
	<sy:updatePeriod>
	hourly	</sy:updatePeriod>
	<sy:updateFrequency>
	1	</sy:updateFrequency>
	<generator>https://wordpress.org/?v=6.8.3</generator>
	<item>
		<title>MySQL添加唯一索引前去除重复数据</title>
		<link>https://www.coder4.com/archives/7025</link>
					<comments>https://www.coder4.com/archives/7025#respond</comments>
		
		<dc:creator><![CDATA[coder4]]></dc:creator>
		<pubDate>Wed, 03 Jun 2020 22:18:15 +0000</pubDate>
				<category><![CDATA[数据库技术]]></category>
		<category><![CDATA[MySQL]]></category>
		<category><![CDATA[去重]]></category>
		<category><![CDATA[唯一索引]]></category>
		<guid isPermaLink="false">https://www.coder4.com/?p=7025</guid>

					<description><![CDATA[delete from YOUR_TABLE where id not in (select id from (select max(id) as id from YOUR_TABLE group by UNIQUE_FIELD) as b); &#160;[......] 继续阅读]]></description>
		
					<wfw:commentRss>https://www.coder4.com/archives/7025/feed</wfw:commentRss>
			<slash:comments>0</slash:comments>
		
		
			</item>
		<item>
		<title>Hive中Group By的去重</title>
		<link>https://www.coder4.com/archives/4007</link>
					<comments>https://www.coder4.com/archives/4007#comments</comments>
		
		<dc:creator><![CDATA[coder4]]></dc:creator>
		<pubDate>Tue, 29 Oct 2013 06:42:31 +0000</pubDate>
				<category><![CDATA[大数据技术]]></category>
		<category><![CDATA[COLLECT_SET]]></category>
		<category><![CDATA[Hive]]></category>
		<category><![CDATA[去重]]></category>
		<guid isPermaLink="false">http://www.coder4.com/?p=4007</guid>

					<description><![CDATA[在Hive的是用中，我们经常会有这种需求： 按照同一个id进行Ｇroup By，然后对另一个字段去重，例如下面得数据： id pic 1 1.jpg 2 2.jpg 1 1.jpg 此时，是用DISTINCT或者2 col得Group By都是不行得，我们可以用这个UDAF：collect_set(col)，它将对同一个group by 得key进行set去重后，转换为一个array。 再举一个例子，我们可以对pic进行去重，拼接： SELECT id, CONCAT_W[......] 继续阅读]]></description>
		
					<wfw:commentRss>https://www.coder4.com/archives/4007/feed</wfw:commentRss>
			<slash:comments>1</slash:comments>
		
		
			</item>
	</channel>
</rss>
