[1]普通方法, 效率太低SELECT * FROM table ORDER BY rand() LIMIT 10;[2] JOIN的方法: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 10;
这个我看过 不过他是对单表操作的如果我是几个表关联后用的 order by rand() 比如select A.a1, A.a2, A.a3, B.b1, B.b2, C.c1 from A left join B on.... left join C on.... where .... order by rand() limit 10这个怎么写?
如果 查询出来的集合有一个字段是连续的就好办了select max(xx) as xx,min(yy) as yy........然后$arr = rand(yy,xx);然后 再select ...... where xxid id implode($arr)
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 10;
比如select A.a1, A.a2, A.a3, B.b1, B.b2, C.c1
from A
left join B on....
left join C on....
where ....
order by rand() limit 10这个怎么写?