thinkphp 按指定字段统计数据条数

 $shops = $Table->field('id , count(weekday) as num')->where($where)->group('weekday')->select();

结果
Array( 
   [0] => Array ( 
         [id] => 1 
          [num] => 3 
  ) 
[1] => Array (
          [id] => 2 
         [num] => 3        
  )  
）