MySQL server error report:Array ( [0] => Array ( [message] => MySQL Query Error ) [1] => Array ( [sql] => select count(1) as num,gtype as nature,cat_name from ecs_types, ecs_goods where is_on_sale=1 and is_delete=0 and cat_id in (21) and ecs_goods.gtype=ecs_types.cat_id group by gtype ) [2] => Array ( [error] => Column 'cat_id' in where clause is ambiguous ) [3] => Array ( [errno] => 1052 ) )