SQL 加了Order By超慢,去掉飞快,怎么解决
- SQL code
SELECT novel_booklist.ID AS aID, novel_chapter.ID AS bID, novel_category.ID AS cID, novel_booklist.Author, novel_booklist.Category, novel_chapter.BookName, novel_chapter.ChapterName, novel_chapter.ID, novel_chapter.UpTime FROM novel_chapter, novel_booklist, novel_category WHERE novel_chapter.BookName = novel_booklist.BookName AND novel_booklist.Category = novel_category.CategoryName ORDER BY novel_chapter.UpTime DESC LIMIT 20
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加了Order By超慢,去掉飞快,怎么解决,加了 ORDER BY novel_chapter.UpTime Desc 执行速度是 1.2ms 去掉后 0.023ms
UpTime也做了索引,不过试了下,UpTime有索引跟没索引速度基本上一样,有何解决办法呢
converting HEAP to MyISAM 1.333%
Copying to tmp table 34.268%
Copying to tmp table on disk 60.152%
——解决方案——————–
创建 (BookName, UpTime)的复合索引
——解决方案——————–
参考一下这个贴子。
http://topic.csdn.net/u/20110827/17/739bd667-703b-4ca1-89ff-e625e724d00b.html
——解决方案——————–
强制索引
select *
from A force index(1楼的索引)
where …
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