Elequent请求中GROUP_CONCAT出错

Question

我想用eloquent（Laravel 4.2）向数据库发出请求..我有GROUP_CONCAT SQL函数的问题：

$articles = Article::join('tags', function ($join) {
            $join->on('articles.id', '=', 'tags.article_id');
        })->get(array('articles.*', 'GROUP_CONCAT(tags.tag_id SEPARATOR ', ') as tags'));

我收到了这个SQL错误：

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'GROUP_CONCAT(tags.tag_id SEPARATOR ' in 'field list' (SQL: select `articles`.*, `GROUP_CONCAT(tags`.`tag_id SEPARATOR `, `)` as `tags` from `articles` inner join `tags` on `articles`.`id` = `tags`.`article_id`

Answer 1

您需要raw expression：

$articles = DB::table('articles')
                ->select(DB::raw('articles.*', 'GROUP_CONCAT(tags.tag_id SEPARATOR ', ') as tags'))
                ->join('tags', function ($join) {
                    $join->on('articles.id', '=', 'tags.article_id');
                })->get();