QEP
Utilizing multiple indexes per MySQL table join
Historically it was considered that MySQL will generally use only one index per referenced table in a SQL query. In MySQL 5.0 the introduction of merge indexes enabled for certain conditions the possibility to utilize two indexes however this could result in worst performance then creating a better index.
Read moreExtra: Using Index
Many people consider this information in the MySQL Query Execution Plan (QEP) to indicate that the referenced table is using an index. It actually means that ONLY the index is used.
Read moreOptimizing UPDATE and DELETE statements
Updated Nov 2011. Check out my latest book on Optimizing SQL Statements for more information. MySQL 5.6.2 also now provides an EXPLAIN syntax for UPDATE and DELETE statements natively. While most people look at performance optimizations for SELECT statements, UPDATE and DELETE statements are often overlooked.
Read moreEXPLAIN – An essential tool for MySQL developers.
Just recently I came across the presentation “Bend SQL to your will with EXPLAIN” by Ligaya Turmelle via the Linked In – MySQL Speakers and Presenters group. Slides available at Slideshare .
Read moreWe need more CATs
Before you think I’ve posted an animal story in my MySQL category please read on. For reference, The RAT and the CAT is something I wrote back in 2006, that explains the CAT part.
Read moreUnderstanding Different MySQL Index Implementations
It is important to know and understand that while indexing columns in MySQL will generally improve performance, using the appropriate type of index can make a greater impact on performance.
Read moreA 5.1 QEP nicety – Using join buffer
I was surprised to find yesterday when using MySQL 5.1.26-rc with a client I’m recommending 5.1 to, some information not seen in the EXPLAIN plan before while reviewing SQL Statements.
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