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mysql怎样高效率随机获取n条数据

时间:2020-05-15 18:24:04      阅读:82      评论:0      收藏:0      [点我收藏+]

标签:and   高效   max   rand   结果   city   方法   order   获取   

ID连续的情况下(注意不能带where,否则结果不好):

SELECT *
FROM `mm_account` AS t1 JOIN (SELECT ROUND(RAND() * (SELECT MAX(id) FROM `mm_account`)) AS id) AS t2
WHERE t1.id >= t2.id
ORDER BY t1.id ASC LIMIT 4;
ID不连续的情况下:

SELECT * FROM `mm_account`
WHERE id >= (SELECT floor(RAND() * (SELECT MAX(id) FROM `mm_account`))) and city="city_91" and showSex=1
ORDER BY id LIMIT 4;

假设你的表叫做mm_account,并且有一个字段叫id。最快的方法如下(随机获取5条):

SELECT * FROM mm_account WHERE id >= ((SELECT MAX(id) FROM mm_account)-(SELECT MIN(id) FROM mm_account)) * RAND() + (SELECT MIN(id) FROM mm_account) limit 5;
如果带where语句,上面就不适合了。带where语句请看下面:

SELECT *
FROM `mm_account` AS t1 JOIN (SELECT ROUND(RAND() * (
(SELECT MAX(id) FROM `mm_account` where id<1000 )-(SELECT MIN(id) FROM `mm_account` where id<1000 ))+(SELECT MIN(id) FROM `mm_account` where id<1000 )) AS id) AS t2
WHERE t1.id >= t2.id
ORDER BY t1.id LIMIT 5;

 

mysql怎样高效率随机获取n条数据

标签:and   高效   max   rand   结果   city   方法   order   获取   

原文地址:https://www.cnblogs.com/hellohorld/p/12896043.html

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