mysql - wpdb 查询的限制结果

Question

此代码仅显示当前类别中的标签，但是它获取所有标签(数百个)，因此，我需要限制返回结果的数量并使它们随机。

如何让这个查询随机只得到 20 个结果？

/* Retrieve all tags from posts in selected categories */

$cats = array('beaches','mountains');  // Must be an array even if only one category
$cats_string = "'" . implode($cats,"','") . "'";
$sql = <<<EOSQL
SELECT DISTINCT t.*
FROM $wpdb->posts p
JOIN $wpdb->term_relationships tr ON p.ID = tr.object_id
JOIN $wpdb->term_taxonomy tt ON (tr.term_taxonomy_id = tt.term_taxonomy_id
   AND tt.taxonomy = 'post_tag')
JOIN $wpdb->terms t ON tt.term_id = t.term_id
WHERE
   p.ID IN (
      SELECT p2.ID
      FROM $wpdb->posts p2
      JOIN $wpdb->term_relationships tr2 ON p2.ID = tr2.object_id
      JOIN $wpdb->term_taxonomy tt2 ON (tr2.term_taxonomy_id = tt2.term_taxonomy_id     AND tt2.taxonomy = 'category')
  JOIN $wpdb->terms t2 ON (tt2.term_id = t2.term_id AND t2.name IN ($cats_string))
  WHERE p2.post_type = 'post'
  AND p2.post_status = 'publish'
  AND p2.post_date <= NOW()
  )
  EOSQL;

$terms = $wpdb->get_results($sql);

// print_r($terms);

echo "<br />";
foreach ($terms as $term) {
   echo "ID:$term->term_id NAME:$term->name SLUG:$term->slug<br />";
}

谢谢

Answer 1

您可以尝试 ORDER BY RAND() LIMIT 20，具体取决于您的表大小，这可以在适当的时间内运行。请参阅here有关何时避免 order by rand() 逻辑的一些详细信息。正如所建议的，在指定的帖子中，另一种方法是检索所有条目并随机选择 20 个条目，在 PHP 中而不是使用 mysql。