Question

大家，

我正在研究一个php和mysql项目，我有一个SQL查询，从我的数据库中选择主题（集合），用户信息表格中包含用户表格和与每个集合相关的标签我使用的查找表就像那样：

select 
        `collections`.`id` as c_id
        , `collections`.`user_id` as c_user_id
        , `thumbnail`
        , left(`collections`.`description`, 81) as description
        , `collections`.`added` as c_added
        , `collections`.`views` as c_views
        , `collections`.`likes` as c_likes
        , `collections`.`title` as c_title
        , `users`.`name` as user_name
        , `users`.`avatar`
        , group_concat(`tags`.`tag_name`) as hashtags
        from collections left join collectionstags 
                    on collections.id = collectionstags.collection_id
        left join tags on 
                    tags.id = collectionstags.tag_id 
        inner join users on
                    `collections`.`user_id` = `users`.`id` 
        group by collections.id 
        order by `collections`.`added` DESC
        limit 0, 16;

它运行正常，它返回我需要的信息，直到我尝试添加另一个左连接以从注释表中获取注释数量：

select 
        `collections`.`id` as c_id
        , `collections`.`user_id` as c_user_id
        , `thumbnail`
        , left(`collections`.`description`, 81) as description
        , `collections`.`added` as c_added
        , `collections`.`views` as c_views
        , `collections`.`likes` as c_likes
        , `collections`.`title` as c_title
        , `users`.`name` as user_name
        , `users`.`avatar`
        , group_concat(`tags`.`tag_name`) as hashtags
        , count(`comments`.`id`) as num_comments
        from collections left join collectionstags 
                    on collections.id = collectionstags.collection_id
        left join tags on 
                    tags.id = collectionstags.tag_id 
        inner join users on
                    `collections`.`user_id` = `users`.`id`
        left join comments on 
                    `comments`.`collection_id` = `collections`.`id`'; 
        group by collections.id 
        order by `collections`.`added` DESC
        limit 0, 16;

当我添加这个最后一个连接时，它开始返回每个标签16次而不是一次，例如而不是返回：

hashtags="nature, river, trees";

它返回：

hashtags="nature, nature, nature, nature, nature, nature, nature, nature, nature, nature, nature, nature, nature, nature, nature, nature, trees,...ect";

Answer 1

请使用group_concat（DISTINCT（tags。tag_name））作为主题标签

SQL查询多次返回group_concat函数中的标记字段

1 个答案: