ty0415的专栏

mysql索引

http://www.cnblogs.com/cocos/archive/2011/05/06/2039469.html

第一种方法和第二种方法相比，效率低很多 SELECT * FROM `table` ORDER BY RAND() LIMIT 5 /*第一种方法*/ SELECT * FROM `table` AS t1 JOIN (SELECT ROUND(RAND() * ((SELECT MAX(id) FROM `table`)-(SELECT MIN(id) FROM `table`))+(

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