原生SQL：
SELECT [ccode],[cbarcode],[cproname],sum(cnum) as cnum
FROM [cart] WHERE ( ([ccreatedate] >= 1406217600) AND ([ccreatedate] <= 1406303999) ) AND ( [cstatus] = 1 )
GROUP BY ccode,cbarcode,cproname;
现在我在TP里面写成:$list = $Product->field('ccode,cbarcode,cproname, sum(cnum) as cnum')->where($where)->order('ccreatedate DESC')->limit($Page->firstRow.','.$Page->listRows)->group('ccode,cbarcode,cproname')->select();
输出SQL语句是对的 但是为什么返回$list是false呢