MySql 语句
在sp表里面有20万条数据 想随机有条件取40条数据居然是随机就不能相同啦目前自己用这方法也能获取但是有点慢好像有时获取出来这条件 视频类型还是错的，select * from `sp` where`视频类型`='游戏' order by rand() limit 40
请问有没有高效率语句。自己菜鸟一个不懂MySql 语句。
百度也百度过来找不到相关问题。求好心人帮忙
22222222 大佬我不会用求教 本帖最后由 tester 于 2020-11-26 16:55 编辑
rand()放在ORDER BY 子句中会被执行多次,20万的数据最少好几秒.
SELECT * FROM `table`
WHERE id >= (SELECT floor(RAND() * (SELECT MAX(id) FROM `table`)))
ORDER BY id LIMIT 1;
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 1;
随机一条的.1改成10,会随机产生10条连续的.
tester 发表于 2020-11-26 16:44
rand()放在ORDER BY 子句中会被执行多次,20万的数据最少好几秒.
SELECT * FROM `table`
WHERE id >= (SELE ...
老哥你这个我百度也看到过 但是看不懂不知道怎么修改 还有这个好像是没有条件的 136444518 发表于 2020-11-26 19:29
老哥你这个我百度也看到过 但是看不懂不知道怎么修改 还有这个好像是没有条件的 ...
怎么修改访问这个sp表条件是视频类型`='游戏 136444518 发表于 2020-11-26 19:31
怎么修改访问这个sp表条件是视频类型`='游戏
table换成sp ,where后面加个and条件呗 tester 发表于 2020-11-26 20:47
table换成sp ,where后面加个and条件呗
SELECT *
FROM `sp` AS t1 JOIN (SELECT ROUND(RAND() * ((SELECT MAX(id) FROM `sp`)-(SELECT MIN(id) FROM `sp`))+(SELECT MIN(id) FROM `sp`)) AS id) AS t2
WHERE t1.id >= t2.id
ORDER BY t1.id LIMIT 1 where`视频类型`='游戏'; 老哥这是哪里错误了 不行啊 136444518 发表于 2020-11-26 23:04
SELECT *
FROM `sp` AS t1 JOIN (SELECT ROUND(RAND() * ((SELECT MAX(id) FROM `sp`)-(SELECT MIN(id) F ...
SELECT *
FROM `sp` AS t1 JOIN (SELECT ROUND(RAND() * ((SELECT MAX(id) FROM `sp`)-(SELECT MIN(id) FROM `sp`))+(SELECT MIN(id) FROM `sp`)) AS id) AS t2
WHERE `视频类型`='游戏' t1.id >= t2.id
ORDER BY t1.id LIMIT 1;这样也不行 ѧϰ
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