使用 MySQL 连接从表中获取值答案

【问题标题】：Get values from the table using MySQL joins使用 MySQL 连接从表中获取值
【发布时间】：2014-08-16 19:38:26
【问题描述】：

在 mysql 中我有 3 个表称为

ps_product_lang

ps_order_detail

and ps_image

这里是表格示例数据

=== ps_product_lang ===


CREATE TABLE IF NOT EXISTS `ps_product_lang` (
  `id_product` int(10) unsigned NOT NULL,
  `id_shop` int(11) unsigned NOT NULL DEFAULT '1',
  `id_lang` int(10) unsigned NOT NULL,
  `description` text,
  `description_short` text,
  `name` varchar(128) NOT NULL,
  PRIMARY KEY (`id_product`,`id_shop`,`id_lang`),
  KEY `id_lang` (`id_lang`),
  KEY `name` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
-- Dumping data for table `ps_product_lang`
--

INSERT INTO `ps_product_lang` (`id_product`, `id_shop`, `id_lang`, `description`, `description_short`,  `name`) VALUES
(1, 1, 1, '<p>this is dummy</p>', '<p>dummy</p>', 'dummy product')
);


===== ps_order_detail===
    CREATE TABLE IF NOT EXISTS `ps_order_detail` (
      `id_order_detail` int(10) unsigned NOT NULL AUTO_INCREMENT,
      `id_order` int(10) unsigned NOT NULL,
      `product_id` int(10) unsigned NOT NULL,
      PRIMARY KEY (`id_order_detail`),
      KEY `product_id` (`product_id`)
    ) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=16 ;

    --
    -- Dumping data for table `ps_order_detail`
    --

    INSERT INTO `ps_order_detail` (`id_order_detail`, `id_order`,  `product_id`) VALUES
    (1, 1, 2);

========= ps_image =========
CREATE TABLE IF NOT EXISTS `ps_image` (
  `id_image` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `id_product` int(10) unsigned NOT NULL,
  `position` smallint(2) unsigned NOT NULL DEFAULT '0',
  `cover` tinyint(1) unsigned NOT NULL DEFAULT '0',
  PRIMARY KEY (`id_image`),
  UNIQUE KEY `idx_product_image` (`id_image`,`id_product`,`cover`),
  KEY `image_product` (`id_product`),
  KEY `id_product_cover` (`id_product`,`cover`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=24 ;

--
-- Dumping data for table `ps_image`
--

INSERT INTO `ps_image` (`id_image`, `id_product`, `position`, `cover`) VALUES
(1, 1, 1, 1),
(2, 1, 2, 0),
(3, 1, 3, 0),
(4, 1, 4, 0),
(5, 2, 1, 0),
(6, 2, 2, 0),
(7, 2, 3, 1),
(8, 3, 1, 1),
(9, 3, 2, 0),
(10, 4, 1, 1),
(11, 4, 2, 0),
(12, 5, 1, 1),
(13, 5, 2, 0),
(14, 5, 3, 0),
(15, 5, 4, 0),
(16, 6, 1, 1),
(17, 6, 2, 0),
(18, 6, 3, 0),
(19, 6, 4, 0),
(20, 7, 1, 1),
(21, 7, 2, 0),
(22, 7, 3, 0),
(23, 7, 4, 0);

所以在这里我想得到所有的字段像

id_order_detail id_product name id_image(from ps_image table where cover = 1)

要获取 id_order_detail id_product name 我正在使用这个 mysql inner join

SELECT DISTINCT (a.id_order_detail),(b.id_product),(b.name)
        FROM ps_order_detail a join 
        ps_product_lang b on a.product_id=b.id_product GROUP BY(name)

这个给我id_order_detail id_product name

现在我想得到id_image from the ps_image table where the cover value is 1 for the product_id

那么有人可以告诉我怎么做吗？任何帮助和建议都将非常可观。谢谢

【问题讨论】：

DISTINCT 如果你有 GROUP BY 是毫无意义的

标签： mysql left-join inner-join

【解决方案1】：

你能不能也加入 product_id 上的第三个表？像这样

SELECT a.id_order_detail, b.id_product, b.name, c.id_image
FROM ps_order_detail a 
join ps_product_lang b on a.product_id=b.id_product 
join ps_image c on c.id_product = a.product_id
where c.cover = 1

【讨论】：