by Peter Zaitsev | Feb 5, 2018 | Insight for DBAs, MySQL
In this blog post, I’ll look into four ways MySQL executes GROUP BY. In my previous blog post, we learned that indexes or other means of finding data might not be the most expensive part of query execution. For example, MySQL GROUP BY could potentially be...
by Peter Zaitsev | Jan 30, 2018 | Insight for DBAs, MySQL
In this blog post, I’ll look at whether optimizing indexing is always the key to improving MySQL query performance (spoiler, it isn’t). As we look at MySQL query performance, our first concern is often whether a query is using the right indexes to retrieve...
by David Ducos | Jun 15, 2015 | MySQL
We usually try to avoid subselects because sometimes they force the use of a temporary table and limits the use of indexes. But, when is good to use a subselect? This example was tested over table a (1310723 rows), b, c and d ( 5 rows each) and with MySQL version 5.5...
