MySQL的 - 从随机列，但获得大量指定

Question

我想做到这一点

SELECT * 
    FROM Thoughts 
ORDER BY RAND() 
LIMIT 1 WHERE ups > 5 

...但它返回一个错误。你知道另一个选择吗？我对MySQL有点新，谢谢。

Answer 1

条款的顺序很重要。不要

SELECT * FROM Thoughts WHERE ups > 5 ORDER BY RAND() LIMIT 1

此外，在未来，发布错误你，你得到。 “一个错误”是惊人的不确定性。

Answer 2

ORDER BY RAND（）可能会导致性能问题，而不是尝试以下办法做到：

// what NOT to do: 
$r = mysql_query("SELECT * FROM Thoughts WHERE ups > 5 ORDER BY RAND() LIMIT 1"); 

// much better: 

$r = mysql_query("SELECT count(*) FROM Thoughts WHERE ups > 5 "); 
$d = mysql_fetch_row($r); 
$rand = mt_rand(0,$d[0] - 1); 

    $r = mysql_query("SELECT * FROM Thoughts WHERE ups > 5 LIMIT $rand, 1");