join($join, $condition = null, $type = 'INNER'); $join : 关联的表名; $condition : 条件; $type : JOIN类型; 用法举例 : ~~~ db('Group')->alias('g') ->join('demo d','g.group_id=d.group_id') ->where("g.uid='$uid' and d.type='$type' and !isnull(extend_id)") ->column('extend_id'); ~~~