Warning: Creating default object from empty value in /www/htdocs/v030397/mysql-qotd/wp-content/plugins/sitepress-multilingual-cms/sitepress.class.php on line 4991
Warning: Creating default object from empty value in /www/htdocs/v030397/mysql-qotd/wp-content/plugins/sitepress-multilingual-cms/sitepress.class.php on line 4993
Warning: Cannot modify header information - headers already sent by (output started at /www/htdocs/v030397/mysql-qotd/wp-content/plugins/sitepress-multilingual-cms/sitepress.class.php:4991) in /www/htdocs/v030397/mysql-qotd/wp-includes/feed-rss2-comments.php on line 8 Comments on: Question 47: Which indexes will help with the performance of the following query?
http://mysql-qotd.casperia.net/archives/354
mysql 5.0/5.1 questions for learning purposesFri, 06 Aug 2010 16:56:36 +0000http://wordpress.org/?v=abchourly1By: plogi
http://mysql-qotd.casperia.net/archives/354/comment-page-1#comment-53
plogiSat, 22 May 2010 13:55:42 +0000http://mysql-qotd.casperia.net/archives/354#comment-53<b>
a b e
a and b decrease execution time drastically with b being the fastest.
e helps (a bit) but the amount of accessed rows is still huge.
d has no effect.
The selectivity of c is very low with 10 different values - the optimizer will use it, but it actually doesn't help.
Try to create each index and explain the query!
</b>
a b e
a and b decrease execution time drastically with b being the fastest.
e helps (a bit) but the amount of accessed rows is still huge.
d has no effect.
The selectivity of c is very low with 10 different values – the optimizer will use it, but it actually doesn’t help.
Try to create each index and explain the query!
]]>