删除总计数百分比

Question

假设我想删除10%的行,是否有查询要执行此操作？

就像是:

DELETE FROM tbl WHERE conditions LIMIT (SELECT COUNT(*) FROM tbl WHERE conditions) * 0.1

Answer 1

我将简单地返回过滤行的总数，通过 php 计算并使用该值作为我的 DELETE 查询中的限制。

$query = mysql_query("SELECT COUNT(*) FROM tbl WHERE conditions");
$int = reset(mysql_fetch_array($query));
$int = round($int * 0.1);

mysql_query("DELETE FROM tbl WHERE conditions LIMIT {$int}");

我不确定 DELETE 是否允许高级查询，如下所示：

DELETE FROM (   SELECT h2.id
                FROM (  SELECT COUNT(*) AS total
                        FROM tbl
                        WHERE conditions) AS h
                JOIN (  SELECT *, @rownum := @rownum + 1 AS rownum
                        FROM tbl, (SELECT @rownum := 0) AS vars
                        WHERE conditions) AS h2
                ON '1'
                WHERE rownum < total * 0.1) AS h3