mysql百万级数据查询,mysql随机查询若干条数据的方法

1.随机读取连续多条记录。经过实践，可以随机读取多条连续的数据记录，里头取值的一般都是主键ID来进行最大值、最小值的读取：

SELECT * FROM example_table AS t1 JOIN (SELECT ROUND(RAND() * ((SELECT MAX(id) FROM example_table)-(SELECT MIN(id) FROM example_table))+(SELECT MIN(id) FROM example_table)) AS id) AS t2 WHERE t1.id >= t2.id ORDER BY t1.id LIMIT 5;

2.随机多条数据。以下两种都是随机读取数据，查询数据速度、随机范围都基本相差不大

SELECT * FROM example_table WHERE id >= ((SELECT MAX(id) FROM example_table)-(SELECT MIN(id) FROM example_table)) * RAND() + (SELECT MIN(id) FROM example_table) LIMIT 5;

SELECT * FROM example_table WHERE id>=(SELECT floor(RAND() * ((SELECT MAX(id) FROM example_table)-(SELECT MIN(id) FROM example_table)) + (SELECT MIN(id) FROM example_table))) ORDER BY id LIMIT 5;