Question

我需要从最新的新闻数据库中提取随机的4个项目。

因为这个表有很多行。通过RAND（）或者浪费资源来做这样的事情是明智的吗？ - 因为它会整个表格并重新排序吗？

有更好的方法吗？从表中提取数百行的随机特色项目？

示例：

$l=$database->query("SELECT car,price,thumbnail FROM cardb WHERE type='new' order by RAND() LIMIT 4");
foreach($l as $l){print_r($l);}

感谢你抽出时间回答 }

Answer 1

嗯......我会在两个查询中执行此操作。获取随机行号：

SELECT
    floor(count * rand()) r1,
    floor(count * rand()) r2,
    floor(count * rand()) r3,
    floor(count * rand()) r4
FROM
    (SELECT count(*) count FROM cardb WHERE type = 'new') c

获取行：

SELECT car, price, thumbnail FROM cardb WHERE type = 'new' LIMIT {r1}, 1
UNION ALL
SELECT car, price, thumbnail FROM cardb WHERE type = 'new' LIMIT {r2}, 1
UNION ALL
SELECT car, price, thumbnail FROM cardb WHERE type = 'new' LIMIT {r3}, 1
UNION ALL
SELECT car, price, thumbnail FROM cardb WHERE type = 'new' LIMIT {r4}, 1

Mysql：'由Rand（）限价4'订购还是没有？

1 个答案: