你要的是meta_query

$args = array(
   \'meta_key\' => \'custom-meta-key\',
   \'meta_query\' => array(
       array(
           \'key\' => \'cp_annonceur\',
           \'value\' => \'professionnel\',
           \'compare\' => \'=\',
       )
   )
);
$query = new WP_Query($args);

有两种方法可以做到这一点：

截取上的主查询pre_get_posts:

add_action( \'pre_get_posts\', function( $query )
{
    // only handle the main query
    if ( ! $query->is_main_query() )
        return;

    $query->set( \'meta_key\',   \'cp_annonceur\' );
    $query->set( \'meta_value\', \'professionnel\' );
} );

$second_loop = get_posts( array(
    \'meta_key\'   => \'cp_annonceur\',
    \'meta_value\' => \'professionnel\',
) );

我使用了自定义选择（性能可能更好）

$posts = $wpdb->get_results("SELECT * FROM $wpdb->postmeta
WHERE meta_key = \'cp_annonceur\' AND  meta_value = \'professionnel\' LIMIT 1", ARRAY_A);

我们可以通过WordPress的元查询获得所需的结果：

// the meta_key \'diplay_on_homepage\' with the meta_value \'true\'
$cc_args = array(
    \'posts_per_page\'   => -1,
    \'post_type\'        => \'post\',
    \'meta_key\'         => \'cp_annonceur\',
    \'meta_value\'       => \'professionnel\'
);
$cc_query = new WP_Query( $cc_args );

您可以使用WordPress的内置函数get_posts您可以找到有关get_posts 在这里https://developer.wordpress.org/reference/functions/get_posts/

$posts = get_posts(array(
    \'numberposts\'   => -1,
    \'post_type\'     => \'post\',
    \'meta_key\'      => \'cp_annonceur\',
    \'meta_value\'    => \'professionnel\'
));

试试这个，对我有用

global $wpdb;
$meta_key = \'_request_body\';

$data = $wpdb->get_results($wpdb->prepare( "SELECT DISTINCT meta_value FROM $wpdb->postmeta WHERE meta_key = %s", $meta_key) , ARRAY_N  );

$result = [];
foreach($data as $array){
    $result[] = $array[0];
}

print_r($result);