… BY implementation “Later one of the clients performing group bys on tens of millions of rows complained and … sum(q.score) score FROM exam e INNER JOIN question q ON e.id = q.exam_id GROUP BY … the group by clause….and MySQL is determined to sort on that column (and then on name should description …
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 19 Comments
…can be happening on Unix at a time. On Windows, InnoDB uses native async I/O, and can perform many read… rows if they were not matched by query where clause when it was not resolved by index HT: …database (for example, if ORDER and ORDERLINE tables are joined to form a single table), it might make …
Comment: How to find wrong indexing with glance view
August 22, 2008 By 27 Comments
… last column I was searching for in my WHERE clause was a string. Here’s how I took that… from my tests it just doesn’t match the performance of indexing an INT, unsigned or not. You can… queries till I attended a presentation by Jay Pipes on Join Fu. (http://www.jpipes.com/) You think this discussion…
Post: MySQL Limitations Part 3: Subqueries
October 25, 2010 By 21 Comments
…the query to make the inner query dependent on the outer query, which could be an optimization… putting a literal list of items in the IN() clause performs fine. It’s only when there is a…performance, or have had it in the past and have fixed it. And many MySQL users have learned to simply write JOINs…
