我有一个Wordpress网站，是在自定义分类法完全实现之前，由第三方web开发人员为2.9版编写的。我们已经升级到最新的wordpress版本3.5。x、 有一个SQL Select查询在Wordpress错误中生成了一系列错误。日志文件。

在此模板中，我们使用了一些自定义分类法。我关心的问题如下：

（wp\\u term\\u taxonomy.taxonomy）作业

这里的一个关键点是not all Wordpress posts are using the taxonomy field jobs. 因此，一些帖子不会有任何与之相关的“工作”术语。

下面是我经常看到的错误

WordPress database error You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use near \'))\' at 
line 9 for query 

  SELECT DISTINCT p.* FROM wp_posts p, wp_terms t, wp_term_taxonomy tt,
  wp_term_relationships tr, wp_terms t2, wp_term_taxonomy tt2, wp_term_relationships tr2
    WHERE p.id = tr.object_id
      AND t.term_id = tt.term_id
      AND tr.term_taxonomy_id = tt.term_taxonomy_id
      AND p.id = tr2.object_id
      AND t2.term_id = tt2.term_id
      AND tr2.term_taxonomy_id = tt2.term_taxonomy_id
      AND (tt.taxonomy = \'category\' AND tt.term_id = t.term_id AND t.term_id = \'22\')
      AND (tt2.taxonomy = \'jobs\' AND tt2.term_id = t2.term_id AND t2.name IN ())

made by require(\'wp-blog-header.php\'), require_once(\'wp-includes/template-loader.php\'),
include(\'/themes/generic/page.php\')

下面是PHP模板文件中的代码片段。

<?
else :
$playlist = 0; $jobs = null; $job = null; $terms = null;
$jobs = wp_get_object_terms( $post->ID, \'jobs\', array(\'fields\'=>\'names\'));
$term_count = 0;
foreach($jobs as $job) :
    if ($term_count > 0) :
        $terms .= ", \'".$job."\'";
    else :  
        $terms .= "\'".$job."\'" ;
    endif;
    $term_count++;
endforeach;
$sql =  "
        SELECT DISTINCT p.* FROM $wpdb->posts p, $wpdb->terms t, $wpdb->term_taxonomy tt, $wpdb->term_relationships tr, $wpdb->terms t2, $wpdb->term_taxonomy tt2, $wpdb->term_relationships tr2
        WHERE p.id = tr.object_id
        AND t.term_id = tt.term_id
        AND tr.term_taxonomy_id = tt.term_taxonomy_id
        AND p.id = tr2.object_id
        AND t2.term_id = tt2.term_id
        AND tr2.term_taxonomy_id = tt2.term_taxonomy_id
        AND (tt.taxonomy = \'category\' AND tt.term_id = t.term_id AND t.term_id = \'22\')
        AND (tt2.taxonomy = \'jobs\' AND tt2.term_id = t2.term_id AND t2.name IN ($terms))
        ";
if (! $results = $wpdb->get_results($sql)) :
?> 

从PHP文件中的逻辑推断，我看到了变量$terms 使用创建NULL 价值A.foreach 循环用于查找jobs 并将其附加到变量$terms. 接下来，SQL Select查询在最后一个AND条件中使用此变量。

如果$terms 变量，则SQL在不存在任何问题的情况下进行评估。

但是如果在$terms 变量是的NULL. 然后，SQL生成一个语法错误。

如何重写以处理NULL 的值$terms 运行SQL查询时的变量？

我希望我问这个问题足够完整。提前感谢您的任何意见。

$args = array(
    \'post_type\' => \'post\',
    \'tax_query\' => array(
        \'relation\' => \'AND\',
        array(
            \'taxonomy\' => \'category\',
            \'field\' => \'id\',
            \'terms\' => array( 22 )
        ),
        array(
            \'taxonomy\' => \'job\',
            \'field\' => \'name\',
            \'terms\' => $terms,
            \'operator\' => \'IN\'
        )
    )
);
$query = new WP_Query( $args );

$terms = \'no terms\';