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> <channel><title>MySQL Diary</title> <atom:link href="http://www.mysqldiary.com/feed/" rel="self" type="application/rss+xml" /><link>http://www.mysqldiary.com</link> <description>Exploring, Sharing and  Discussing MySQL practice</description> <lastBuildDate>Thu, 02 May 2013 08:42:31 +0000</lastBuildDate> <language>en-US</language> <sy:updatePeriod>hourly</sy:updatePeriod> <sy:updateFrequency>1</sy:updateFrequency> <generator>http://wordpress.org/?v=3.5.1</generator> <item><title>MySQL Left Join</title><link>http://www.mysqldiary.com/mysql-left-join/</link> <comments>http://www.mysqldiary.com/mysql-left-join/#comments</comments> <pubDate>Wed, 06 Jul 2011 09:23:47 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[Cool MySQL Queries]]></category> <category><![CDATA[is null]]></category> <category><![CDATA[left join]]></category> <category><![CDATA[on]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=234</guid> <description><![CDATA[Even if you think you know everything about LEFT JOIN, I bet you will learn something or two in this post! The difference between the ON clause and the WHERE clause. A simple way to better understand a complex Matching-Condition with WHERE … IS NULL clause. The difference between the Matching-Conditions and the Where-conditions. A [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/mysql-left-join/feed/</wfw:commentRss> <slash:comments>10</slash:comments> </item> <item><title>As restoring a dump table into the MySQL master &#8211; you better get some sleep</title><link>http://www.mysqldiary.com/as-restoring-a-dump-table-into-the-mysql-master-you-better-get-some-sleep/</link> <comments>http://www.mysqldiary.com/as-restoring-a-dump-table-into-the-mysql-master-you-better-get-some-sleep/#comments</comments> <pubDate>Mon, 04 Apr 2011 08:09:45 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[Cool MySQL Queries]]></category> <category><![CDATA[MySQL Script]]></category> <category><![CDATA[mysqldump]]></category> <category><![CDATA[sleep]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=198</guid> <description><![CDATA[Restoring a dump table into the MySQL master server can lead to serious replication delay. The massive inserts commands cause the Master and slaves to use most of their resources for replication. As a result, replication lag may increase dramatically (linear to the table size). To overcome the replication delay, caused by restoring the dump [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/as-restoring-a-dump-table-into-the-mysql-master-you-better-get-some-sleep/feed/</wfw:commentRss> <slash:comments>4</slash:comments> </item> <item><title>If you copy a MyISAM table with PRIMARY key, don’t forget to order the rows first</title><link>http://www.mysqldiary.com/if-you-copy-a-myisam-table-with-primary-key-don%e2%80%99t-forget-to-order-the-rows-first/</link> <comments>http://www.mysqldiary.com/if-you-copy-a-myisam-table-with-primary-key-don%e2%80%99t-forget-to-order-the-rows-first/#comments</comments> <pubDate>Mon, 14 Mar 2011 19:02:23 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[Cool MySQL Queries]]></category> <category><![CDATA[MySQL feature]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=189</guid> <description><![CDATA[In a case that you copy (INSERT INTO .. SELECT ..) a MyISAM table that have a PRIMARY key, it is much faster to insert the new rows in the primary key order: The insertion will be faster: because the primary key cannot disabled, every insertion will also updates the primary key. In a case [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/if-you-copy-a-myisam-table-with-primary-key-don%e2%80%99t-forget-to-order-the-rows-first/feed/</wfw:commentRss> <slash:comments>2</slash:comments> </item> <item><title>You Must Have A Killer In Your System</title><link>http://www.mysqldiary.com/you-must-have-a-killer-in-your-system/</link> <comments>http://www.mysqldiary.com/you-must-have-a-killer-in-your-system/#comments</comments> <pubDate>Tue, 08 Feb 2011 16:10:18 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[MySQL Script]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=181</guid> <description><![CDATA[Every system can have a slow query that randomly seems to emerge from nowhere. The main threat from these slow queries is that it can unexpectedly bring down your site. Even though the query is not called often (less than one percent), it can definitely harm your site performance. That is why you should have [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/you-must-have-a-killer-in-your-system/feed/</wfw:commentRss> <slash:comments>2</slash:comments> </item> <item><title>A many to many relationship table – solving the exclude relation problem</title><link>http://www.mysqldiary.com/a-many-to-many-relationship-table-solving-the-exclude-relation-problem/</link> <comments>http://www.mysqldiary.com/a-many-to-many-relationship-table-solving-the-exclude-relation-problem/#comments</comments> <pubDate>Tue, 18 Jan 2011 12:36:07 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[Cool MySQL Queries]]></category> <category><![CDATA[exclude]]></category> <category><![CDATA[inner query]]></category> <category><![CDATA[many to many]]></category> <category><![CDATA[pivot]]></category> <category><![CDATA[relation]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=138</guid> <description><![CDATA[A MySQL many to many relationship is a relationship that is multi-valued in both directions. Given that, how can you select rows that don&#8217;t have a specific relationship (the exclude relation problem)? I will start by defining the MySQL Many to Many relationship (Experts can skip to the next paragraph) What is A MySQL many [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/a-many-to-many-relationship-table-solving-the-exclude-relation-problem/feed/</wfw:commentRss> <slash:comments>9</slash:comments> </item> <item><title>The battle between FORCE INDEX and the QUERY OPTIMIZER</title><link>http://www.mysqldiary.com/the-battle-between-force-index-and-the-query-optimizer/</link> <comments>http://www.mysqldiary.com/the-battle-between-force-index-and-the-query-optimizer/#comments</comments> <pubDate>Mon, 25 Oct 2010 21:15:41 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[Cool MySQL Queries]]></category> <category><![CDATA[MySQL feature]]></category> <category><![CDATA[analyze table]]></category> <category><![CDATA[Cardinality]]></category> <category><![CDATA[Force Index]]></category> <category><![CDATA[key distributions]]></category> <category><![CDATA[MySQL optimizer]]></category> <category><![CDATA[QUERY OPTIMIZER]]></category> <category><![CDATA[Use Index]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=146</guid> <description><![CDATA[Query Optimizer is a part of the server that takes a parsed SQL query and produces a query execution plan. MySQL Query Optimizer uses (as one of its parameters) the stored key distribution (Cardinality) mechanism to determine the order in which tables should be joined, when you perform a join on something other than a [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/the-battle-between-force-index-and-the-query-optimizer/feed/</wfw:commentRss> <slash:comments>2</slash:comments> </item> <item><title>Optimizing the MySQL IN() Comparison Operations Which Include the Indexed Field</title><link>http://www.mysqldiary.com/optimizing-the-mysql-in-comparison-operations-which-include-the-indexed-field/</link> <comments>http://www.mysqldiary.com/optimizing-the-mysql-in-comparison-operations-which-include-the-indexed-field/#comments</comments> <pubDate>Thu, 07 Oct 2010 12:06:13 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[Cool MySQL Queries]]></category> <category><![CDATA[Comparison operator]]></category> <category><![CDATA[IN]]></category> <category><![CDATA[MySQL IN]]></category> <category><![CDATA[performance]]></category> <category><![CDATA[query]]></category> <category><![CDATA[union all]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=128</guid> <description><![CDATA[The MySQL IN() Comparison Operator is said to be very quick if all the values are constants (the values are then evaluated and sorted first, and the search is done using a binary search). However, what if the field which the IN clause refers to, is part of the index used to execute the query? [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/optimizing-the-mysql-in-comparison-operations-which-include-the-indexed-field/feed/</wfw:commentRss> <slash:comments>7</slash:comments> </item> <item><title>MySQL User Defined Variables</title><link>http://www.mysqldiary.com/user-defined-variables/</link> <comments>http://www.mysqldiary.com/user-defined-variables/#comments</comments> <pubDate>Wed, 02 Jun 2010 21:04:19 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[MySQL feature]]></category> <category><![CDATA[case sensitivity]]></category> <category><![CDATA[mysql features]]></category> <category><![CDATA[mysql query]]></category> <category><![CDATA[procedural logic]]></category> <category><![CDATA[relational logic]]></category> <category><![CDATA[User defined variable]]></category> <category><![CDATA[variables]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=7</guid> <description><![CDATA[When I have discovered MySQL User-defined variables at the first time, I didn&#8217;t pay much attention to them and didn&#8217;t realize their strength. At first, one can think that they are just one of the many unnoticed MySQL features. Well, I was wrong. Here, I will try to summarize their strength, though I think there is [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/user-defined-variables/feed/</wfw:commentRss> <slash:comments>29</slash:comments> </item> <item><title>Limited SELECT count(*)</title><link>http://www.mysqldiary.com/limited-select-count/</link> <comments>http://www.mysqldiary.com/limited-select-count/#comments</comments> <pubDate>Thu, 13 May 2010 21:52:43 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[Cool MySQL Queries]]></category> <category><![CDATA[count(*)]]></category> <category><![CDATA[limit]]></category> <category><![CDATA[limited count]]></category> <category><![CDATA[performance]]></category> <category><![CDATA[select]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=98</guid> <description><![CDATA[A SELECT statement with COUNT returns the number of rows retrieved by the SELECT statement (see mysql select count). For performance reasons, the desired result is to limit that count. Including a LIMIT clause in the SELECT statement will not work since it only restricts the number of rows returned, which is always one. The [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/limited-select-count/feed/</wfw:commentRss> <slash:comments>24</slash:comments> </item> <item><title>Conditional Joins in MySQL</title><link>http://www.mysqldiary.com/conditional-joins-in-mysql/</link> <comments>http://www.mysqldiary.com/conditional-joins-in-mysql/#comments</comments> <pubDate>Sun, 07 Feb 2010 19:43:12 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[Cool MySQL Queries]]></category> <category><![CDATA[conditional join]]></category> <category><![CDATA[join in Mysql]]></category> <category><![CDATA[left join]]></category> <category><![CDATA[mysql join]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=71</guid> <description><![CDATA[One way to do a “Conditional Join” in MySQL is by using a “LEFT JOIN”.  Create a “LEFT JOIN” for each condition and combine the results into one column using an “IF” statement by the “SELECT” expression.  Here’s an example: Suppose you have three tables: questions: a table consisting of question ids, timestamps, and whether [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/conditional-joins-in-mysql/feed/</wfw:commentRss> <slash:comments>9</slash:comments> </item> <item><title>Selecting records from one table that dont have specific relationship in a second table</title><link>http://www.mysqldiary.com/selecting-records-from-one-table-that-dont-have-specific-relationship-in-a-second-table/</link> <comments>http://www.mysqldiary.com/selecting-records-from-one-table-that-dont-have-specific-relationship-in-a-second-table/#comments</comments> <pubDate>Sun, 17 Jan 2010 19:57:07 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[Cool MySQL Queries]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=58</guid> <description><![CDATA[Question: How can you select records from one table that doesn’t have a specific ID in a second, many-to-many table?   In other words, imagine you have a questions table (A), categories table (B), and a many-to-many relationship link table (L).  This setup allows a question to have several categories.  How can you find questions that [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/selecting-records-from-one-table-that-dont-have-specific-relationship-in-a-second-table/feed/</wfw:commentRss> <slash:comments>6</slash:comments> </item> <item><title>The fading of Query Cache limitations</title><link>http://www.mysqldiary.com/the-fading-of-query-cache-limitation/</link> <comments>http://www.mysqldiary.com/the-fading-of-query-cache-limitation/#comments</comments> <pubDate>Tue, 15 Dec 2009 19:31:42 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[MySQL feature]]></category> <category><![CDATA[MySQL Query Cache]]></category> <category><![CDATA[Query Cache improvements]]></category> <category><![CDATA[Query Cache limitations]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=50</guid> <description><![CDATA[There is no question about the MySQL Query Cache greatness.  The MySQL Query Cache feature started his way with some limitations.  However, in time, there were a lot of improvements (fixing) for those limitations. One should test his MySQL version with the Query Cache limitations before using it. Here are some improved limitations I found [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/the-fading-of-query-cache-limitation/feed/</wfw:commentRss> <slash:comments>4</slash:comments> </item> <item><title>How to retain comments in MySQL statements</title><link>http://www.mysqldiary.com/how-to-retain-comments/</link> <comments>http://www.mysqldiary.com/how-to-retain-comments/#comments</comments> <pubDate>Thu, 03 Dec 2009 16:09:16 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[MySQL configuration]]></category> <category><![CDATA[bash script]]></category> <category><![CDATA[comment]]></category> <category><![CDATA[inline comment]]></category> <category><![CDATA[retain comments]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=44</guid> <description><![CDATA[There is a lot of buzz lately around retaining comments in MySQL’s logs and MySQL Stored procedures (Routines). When analyzing a MySQL query, it’s nice to have a comment inside the query (or procedure) that can provide us with more info about the query. For example, When analyzing MySQL’s logs (like Slow Query Log or [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/how-to-retain-comments/feed/</wfw:commentRss> <slash:comments>11</slash:comments> </item> <item><title>How to produce random rows from a table</title><link>http://www.mysqldiary.com/how-to-produce-random-rows-from-a-table/</link> <comments>http://www.mysqldiary.com/how-to-produce-random-rows-from-a-table/#comments</comments> <pubDate>Sun, 29 Nov 2009 04:10:30 +0000</pubDate> <dc:creator>Hazan Ilan</dc:creator> <category><![CDATA[Cool MySQL Queries]]></category> <guid
isPermaLink="false">http://www.mysqldiary.com/?p=20</guid> <description><![CDATA[A while ago, I were searching for a way to produce random rows from a table in MySQL. I found several solutions but none of them satisfied me. Of course, I could use  a combined logic of MySQL and a programming language. For example by producing random numbers in PHP and using them in the MySQL query in a IN clouse.  However, I [...]]]></description> <wfw:commentRss>http://www.mysqldiary.com/how-to-produce-random-rows-from-a-table/feed/</wfw:commentRss> <slash:comments>19</slash:comments> </item> </channel> </rss>
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