… Features in MySQL 5.6 Garrick Peterson, a member of Percona’s RemoteDBA team, will talk about MHA for MySQL High Availability in the… be held at Portland State University’s Smith Memorial Student Union, located at 1825 SW Broadway, Suite 327/8/9 Portland… join the Portland MySQL Meetup group for more MySQL-focused events in Portland If you love the ideal of Percona MySQL University and would…
Post: Percona MySQL University @Portland: June 17
May 22, 2013 By 1 Comment
…. Percona MySQL University is a daylong, free, fast-paced and very technical MySQL educational event for wide range of people interested in MySQL – Developers, System Administrators, DBAs, etc. It will be held at Portland State University’s Smith Memorial Student Union. We…
Post: SELECT UNION Results INTO OUTFILE
September 14, 2011 By Leave a Comment
… | | NULL | UNION RESULT | | ALL | NULL | NULL | NULL | NULL | NULL | | +—-+————–+————–+——-+—————+———–+———+——+——+————-+ 5 rows in set (0.00 sec) Compared to using UNION simply: mysql [localhost] {msandbox} (employees) > EXPLAIN SELECT * -> FROM employees -> WHERE hire_date BETWEEN ’1990-01-01′ AND ’1990-01-02′ -> UNION…
Post: MySQL 5.5 and MySQL 5.6 default variable values differences
February 21, 2013 By 8 Comments
… ON by default in MySQL 5.6 but you can see many options can be scaled down compared to MySQL 5.5 default… are less than 200 tables in this system. innodb_stats_on_metadata is disabled by default in MySQL 5.6 Welcome to much…_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on 1 row in set (0.00 sec) mysql…
Post: MySQL Indexing Best Practices: Webinar Questions Followup
August 16, 2012 By 4 Comments
…’ The other thing you need to consider is string comparison in MySQL is case insensitive by default while hash comparison will be… index. In this case you can use trick mentioned in the presentation to convert sort to the union for small ranges. Q: In the… this column. This works because by scanning data in index order MySQL gets data in already sorted order and looks at “one group…
Post: Moving Subtrees in Closure Table Hierarchies
February 14, 2011 By 18 Comments
….length+1 FROM TreePaths AS t WHERE t.descendant = ‘C’ UNION ALL SELECT ‘D’, ‘D’, 0; The above is the simple… descendant IN (SELECT descendant FROM TreePaths WHERE ancestor = ‘D’) AND ancestor NOT IN (SELECT descendant FROM TreePaths WHERE ancestor = ‘D’); But MySQL complains… update in FROM clause.” We can’t DELETE and SELECT from the same table in a single query in MySQL. But we can use MySQL…
Post: UNION vs UNION ALL Performance
October 5, 2007 By 15 Comments
… performance of UNION vs MySQL 5.0 index merge algorithm Sinisa pointed out I should be using UNION ALL instead of simple UNION in my… also tried this original query (which uses index merge method in MySQL 5.0): select * from test.abc where i=5 or… UNION ALL require temporary table can only be seen in SHOW STATUS – EXPLAIN does not want to tell you this shameful fact: mysql…
Post: MySQL: Followup on UNION for query optimization, Query profiling
August 14, 2006 By 14 Comments
…union. So changing query to: mysql> SELECT sql_no_cache name FROM people WHERE age in(18,19,20) AND zip IN… 1 row in set (0.00 sec) So as you see there are really different types of ranges in MySQL. IN range …
Post: Using UNION to implement loose index scan in MySQL
August 10, 2006 By 15 Comments
… give a hand to MySQL Optimizer and change the query so it can handle it well…. use UNION: mysql> SELECT name FROM people WHERE age=18 AND zip IN (12345,12346, 12347) -> UNION ALL -> SELECT name FROM people WHERE age=19 AND zip IN (12345,12346, 12347) -> UNION ALL -> SELECT…
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
… points you need to attack the right query in the right way. But vanilla MySQL does have its limitations, it reports only… to enable logging atomically, not just for new connections as in MySQL. This is very helpful for measurement as otherwise we might… 2.5% 51 0.0039 1.00 0.00 SELECT UNION wp_pp_daily_summary wp_pp_hourly_summary wp_pp…
