php mysql怎么随机获取几条数据

本文操作环境：windows7系统、PHP7.1版、Dell G3电脑。

php mysql怎么随机获取几条数据?

Mysql实现随机获取几条数据的方法

sql语句有几种写法：

SELECT * FROM tablename ORDER BY RAND() LIMIT 想要获取的数据条数；

SELECT *FROM `table` WHERE id >= (SELECT FLOOR( MAX(id) * RAND()) FROM `table` ) ORDER BY id LIMIT 想要获取的数据条数;

SELECT * FROM `table` AS t1 JOIN (SELECT ROUND(RAND() * (SELECT MAX(id) FROM `table`)) AS id) AS t2 WHERE t1.id >= t2.id

ORDER BY t1.id ASC LIMIT 想要获取的数据条数;

SELECT * FROM `table`WHERE id >= (SELECT floor(RAND() * (SELECT MAX(id) FROM `table`))) ORDER BY id LIMIT 想要获取的数据条数;

SELECT * FROM `table` WHERE id >= (SELECT floor( RAND() * ((SELECT MAX(id) FROM `table`)-(SELECT MIN(id) FROM `table`)) + (SELECT MIN(id) FROM `table`))) ORDER BY id LIMIT 想要获取的数据条数;

SELECT * FROM `table` AS t1 JOIN (SELECT ROUND(RAND() * ((SELECT MAX(id) FROM `table`)-(SELECT MIN(id) FROM `table`))+(SELECT MIN(id) FROM `table`)) AS id) AS t2 WHERE t1.id >= t2.id ORDER BY t1.id LIMIT 想要获取的数据条数;

反馈：

实测 38万数据，随机取10条 1 可以随机取值，执行时间1-2秒。 2 运行超过20秒没反应，试了3次。 3 取的10条数据是连续的ID，执行0.001秒。 4 随机取10条，id在1-4000之间，执行0.003秒，试了10次以上。 5 随机取10条，id在1-4000之间，执行0.003秒，试了10次以上。 6 取的10条数据是连续的ID，执行0.001秒。