mysql随机取数据

最新推荐文章于 2023-03-15 15:11:42 发布

Mapleth

最新推荐文章于 2023-03-15 15:11:42 发布

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分类专栏： mysql 文章标签： mysql 随机

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<span style="color: rgb(70, 70, 70); font-family: Verdana, 'BitStream vera Sans', Helvetica, sans-serif; font-size: 13px; line-height: 20.799999237060547px;">从数据表随机获取N条数据记录的方法有很多，其中最简单的莫过于SELECT * FROM `table` WHERE 1 ORDER BY rand() LIMIT N 这个语句得好处在于简单，但前提条件是查询的结果集必须小于5W记录集的情况下方可使用，若数据结果集超过了5W，其查询出来的速度将非常的耗资源。</span>

SELECT * FROM `baidu` AS k1 JOIN (
    SELECT ROUND( RAND( ) * (
        (SELECT MAX( id ) FROM `baidu` ) - (SELECT MIN( id ) FROM `baidu` ) ) +
            (SELECT MIN( id ) FROM `baidu` )) AS id
         ) AS k2
    WHERE k1.id >= k2.id LIMIT 10

0.0445秒 连续记录

 

SELECT * FROM `baidu`
WHERE id >= (floor(RAND() * (SELECT MAX(id) FROM `baidu`)))
ORDER BY id LIMIT 10;

 0.0710 不连续

 

SELECT *
FROM `baidu` AS t1 JOIN (SELECT ROUND(RAND() * ((SELECT MAX(id) FROM `baidu`)-(SELECT MIN(id) FROM `baidu`))+(SELECT MIN(id) FROM `baidu`)) AS id) AS t2
WHERE t1.id >= t2.id
ORDER BY t1.id LIMIT 10;
0.0203 连续的

SELECT * FROM `baidu`
WHERE id >= (SELECT floor( RAND() * ((SELECT MAX(id) FROM `baidu`)-(SELECT MIN(id) FROM `baidu`)) + (SELECT MIN(id) FROM `baidu`)))
ORDER BY id LIMIT 10;
0.0668 不连续