PHP MySQL LEFT JOIN不起作用

Question

我想知道是否有人能帮我解决这个问题。

Example Table ($tableTerms):
-----------------------------
| NAME        | SLUG        |
-----------------------------
| Dean        | dean        |
-----------------------------
| Football    | football    |
-----------------------------

我正在尝试从表$ tableTerms中的“name”列中获取一些数据。

在查询期间，我将列调为“slug”，以便查找“Dean”参加的正确“event_name”。 然后在同一个查询中我想调用列（“名称”），但这次访问行“足球”，这样我就可以看到“Dean”参加的事件类型。

我正在使用Wordpress的术语和分类法，这就是为什么同一个表中有不同类型的数据。

我试图用LEFT JOIN实现我的目标，但我没有运气。 在我添加LEFT JOIN和额外的SELECT之前查询工作，但我现在需要额外的数据。

任何人的帮助都会很棒，谢谢！

院长。

    // Look Up Events Attended
    $tableTerms = $wpdb->prefix . "terms";
    $tableTermTaxonomy = $wpdb->prefix . "term_taxonomy";
    $tableTermRelationships = $wpdb->prefix . "term_relationships";
    $tableEvents = $wpdb->prefix . "em_events";
    $tableEventLocations = $wpdb->prefix . "em_locations";
    $tableEventsMeta = $wpdb->prefix . "em_meta";

    $slug = strtolower($firstName)."-".strtolower($lastName);

    if(isset($memberID)) {  
        $eventsAttendedQuery = $wpdb->get_results("

        SELECT 
        event_name,
        event_start_date,
        location_name,
        tableTermsCategory.name

        FROM  
        $tableTerms,
        $tableTermTaxonomy,
        $tableTermRelationships,
        $tableEvents,
        $tableEventLocations

            LEFT JOIN
            $tableTerms AS tableTermsCategory
            ON tableTermsCategory.term_id = $tableTermTaxonomy.term_id AND
            $tableTermTaxonomy.taxonomy = 'event-categories' AND
            $tableTermTaxonomy.term_taxonomy_id = $tableTermRelationships.term_taxonomy_id AND
            $tableTermRelationships.object_id = $tableEvents.post_id


        WHERE 
        YEAR(event_start_date) = $year AND
        slug = '$slug' AND 
        $tableTerms.term_id = $tableTermTaxonomy.term_id AND
        $tableTermTaxonomy.taxonomy = 'event-tags' AND
        $tableTermRelationships.term_taxonomy_id = $tableTermTaxonomy.term_taxonomy_id AND
        $tableEvents.post_id = $tableTermRelationships.object_id AND
        $tableEvents.location_id = $tableEventLocations.location_id

        ORDER BY event_start_date ASC

        ");

    }

Answer 1

查看您的查询，看看JOINS是否已经完成了。 修改您的查询，如下所示

    SELECT 
    event_name,
    event_start_date,
    location_name,
    tableTermsCategory.name

    FROM  
    $tableTerms LEFT JOIN $tableTermTaxonomy ON $tableTerms.term_id = $tableTermTaxonomy.term_id
    AND $tableTermTaxonomy.taxonomy IN ('event-categories', 'event-tags') 
    AND $tableTermTaxonomy.term_taxonomy_id = $tableTermRelationships.term_taxonomy_id
    LEFT JOIN $tableTermRelationships ON $tableTermRelationships.term_taxonomy_id = $tableTermTaxonomy.term_taxonomy_id
    LEFT JOIN $tableEvents ON $tableEvents.post_id = $tableTermRelationships.object_id
    LEFT JOIN $tableEventLocations ON $tableEvents.location_id = $tableEventLocations.location_id

    WHERE 
    YEAR(event_start_date) = $year AND
    slug = '$slug'
    ORDER BY event_start_date;