MySQL select sum with group by提供整数结果

我有两张桌子：

CREATE TABLE `product_det` (
  `id` bigint(12) unsigned NOT NULL AUTO_INCREMENT,
  `prod_name` varchar(64) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

INSERT INTO `product_det` (`id`,`prod_name`) VALUES 
 (1,'Pepper'),
 (2,'Salt'),
 (3,'Sugar');

CREATE TABLE `product_oper` (
  `id` bigint(12) unsigned NOT NULL AUTO_INCREMENT,
  `prod_id` bigint(12) unsigned NOT NULL,
  `prod_quant` decimal(16,4) NOT NULL DEFAULT '1.0000',
  `prod_value` decimal(18,2) NOT NULL DEFAULT '0.00',
  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

INSERT INTO `product_oper` (`id`,`prod_id`,`prod_quant`,`prod_value`) VALUES 
 (12,2,'3.0000','26.14'),
 (13,2,'0.0450','26.23'),
 (14,2,'0.0300','26.14'),
 (10,1,'0.0600','13.20'),
 (11,1,'0.0600','13.20');

我想在第二个表中求出每种产品的数量和价值

我的问题是：

SELECT product_det.*, SUM(in_out.p_q) as q, SUM(in_out.p_val) AS val
 FROM
 (SELECT product_oper.prod_id as p_id, SUM(product_oper.prod_quant) as p_q, SUM(product_oper.prod_quant*product_oper.prod_value) as p_val
   FROM product_oper
   GROUP BY product_oper.prod_id
 ) AS in_out
 LEFT JOIN product_det ON in_out.p_id=product_det.id
 GROUP BY in_out.p_id
 HAVING q<>0.00  ORDER BY val;

这是错误的，列

val

中的值是整数，不应该是整数

但是，内部选择将给出下一个结果：

p_id,    p_q,     p_val
1,    0.1200,   1.584000
2,    3.0750,  80.384550

问题是：当我从子查询中选择时，为什么会得到

val

的整数值？为什么

q

不是整数

我需要使用子查询，因为我的原始查询是这样的：

SELECT ... FROM (SELECT ... UNION SELECT ...) AS in_out GROUP BY in_out.p_id

---

我有MySQL版本5.1.39

您是否尝试将字段强制转换为十进制？不幸的是，float不可用，但decimal来自版本5.0.8

SELECT product_det.*, SUM(in_out.p_q) as q, SUM(CAST(in_out.p_val AS DECIMAL)) AS val

在内部选择

...CAST(SUM(product_oper.prod_quant*product_oper.prod_value) AS DECIMAL) as p_val...

只是一个想法

...CAST(SUM(product_oper.prod_quant*product_oper.prod_value) AS DECIMAL) as p_val...