> `groupby`用于对数据集合进行分组，例如： ```php //查询订单表中每个用户的订单总额 Db('order')->select([ 'field' => ['SUM(OrderPrice) as Price','userId'], 'groupby' => 'userId' ])->get(); //sql：SELECT SUM(OrderPrice) as Price,`userId` FROM `order` GROUP BY userId; ``` >SQL小技巧：对于查询频率高的多数据表，建立字段索引将大大提高查询速度