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我需要编写一个查询来从每个商家那里获取最低价格并输出价格链接（p_link）和一些其他信息，例如商家名称+评级。

我们有一个价格表 (tgmp_prices)、一个商家表 (tgmp_merchants) 和一个附属产品 ID 表 (tgmp_affiliates)

我已经得到查询来获取我需要的所有价格和数据：

SELECT p_id, p_m_id, p_prod_label, a_platform, p_link, p_price, m_title, m_link, m_avg_rating 
FROM tgmp_affiliates ga 
JOIN tgmp_prices p 
    ON ga.a_code = p.p_gtin 
        AND ga.a_code != '' 
JOIN tgmp_merchants m 
    ON m.m_id = p.p_m_id 
WHERE ga.site_id = '34' 
    AND p.site_id = '34' 
    AND ga.a_parent = '25573' 
    AND p_type = 'games' 
    AND m.m_hide = 0 
ORDER BY p.p_price ASC

我只需要按商家 ID（p.p_m_id 或 m.m_id）对价格进行分组，然后为每个商家选择最低价格。

SELECT p_id, p_m_id, p_prod_label, a_platform, p_link, p_price, m_title, m_link, m_avg_rating 
FROM tgmp_affiliates ga 
JOIN tgmp_prices p 
    ON ga.a_code = p.p_gtin 
        AND ga.a_code != '' 
JOIN tgmp_merchants m 
    ON m.m_id = p.p_m_id 
WHERE ga.site_id = '34' 
    AND p.site_id = '34' 
    AND ga.a_parent = '25573' 
    AND p_type = 'games' 
    AND m.m_hide = 0 
GROUP BY m.m_id
ORDER BY p.p_price ASC

如果我在 ORDER BY 之前添加 GROUP BY m.m_id 我会得到 16 个结果，每个商家 1 个。我只需要使这个价格最低。所以我尝试添加一个子查询，其中价格表（tgmp_prices）是这样连接的：

SELECT p_id, p_m_id, p_prod_label, a_platform, p_link, p_price, m_title, m_link, m_avg_rating 
FROM tgmp_affiliates ga 
JOIN tgmp_prices p 
    ON ga.a_code = p.p_gtin 
        AND ga.a_code != '' 
        AND p.p_price = ( 
            SELECT MIN(p.p_price) 
            FROM tgmp_prices 
            WHERE p.p_m_id = m.m_id
        ) 
JOIN tgmp_merchants m 
    ON m.m_id = p.p_m_id 
WHERE ga.site_id = '34' 
    AND p.site_id = '34' 
    AND ga.a_parent = '25573' 
    AND p_type = 'games' 
    AND m.m_hide = 0 
GROUP BY m.m_id
ORDER BY p.p_price ASC

这并没有给我正确的结果 - 我认为问题可能是运行子查询时 m.m_id 不可用，所以我尝试在子查询中加入商家表，但我仍然结束具有相同的结果集。

DDL如下：

CREATE TABLE IF NOT EXISTS `tgmp_affiliates` (
    `a_id` int(8) NOT NULL AUTO_INCREMENT,
    `site_id` int(6) NOT NULL,
    `a_parent` int(8) NOT NULL,
    `a_code` varchar(32) NOT NULL,
    `a_type` varchar(32) NOT NULL,
    `a_platform` varchar(12) NOT NULL,
    PRIMARY KEY (`a_id`),
    UNIQUE KEY `site_id` (`site_id`,`a_parent`,`a_code`,`a_type`,`a_platform`),
    KEY `a_code` (`a_code`),
    KEY `a_parent` (`a_parent`),
    KEY `a_platform` (`a_platform`),
    KEY `a_type` (`a_type`),
    KEY `site_id_2` (`site_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 ;

-- --------------------------------------------------------

--
-- Table structure for table `tgmp_merchants`
--

CREATE TABLE IF NOT EXISTS `tgmp_merchants` (
    `m_id` int(8) NOT NULL AUTO_INCREMENT,
    `site_id` int(6) NOT NULL,
    `m_title` varchar(128) NOT NULL,
    `m_url` text NOT NULL,
    `m_link` varchar(128) NOT NULL,
    `m_favicon` text NOT NULL,
    `m_avg_rating` tinyint(1) NOT NULL,
    `m_hide` tinyint(1) NOT NULL DEFAULT '0',
    PRIMARY KEY (`m_id`),
    UNIQUE KEY `m_title` (`m_title`,`m_link`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 ;

-- --------------------------------------------------------

--
-- Table structure for table `tgmp_prices`
--

CREATE TABLE IF NOT EXISTS `tgmp_prices` (
    `p_id` int(8) NOT NULL AUTO_INCREMENT,
    `site_id` int(6) NOT NULL,
    `p_m_id` int(8) NOT NULL,
    `p_prod_label` varchar(128) NOT NULL,
    `p_gtin` varchar(64) NOT NULL,
    `p_parent` int(8) NOT NULL,
    `p_link` text NOT NULL,
    `p_price` decimal(8,2) NOT NULL,
    `p_delivery` decimal(8,2) NOT NULL,
    `p_currencey` varchar(10) NOT NULL,
    `p_avail` varchar(32) NOT NULL,
    `p_condition` varchar(32) NOT NULL,
    `p_when` datetime NOT NULL,
    `p_type` varchar(32) NOT NULL,
    `p_hide` tinyint(1) NOT NULL DEFAULT '0',
    PRIMARY KEY (`p_id`),
    UNIQUE KEY `p_gtin` (`p_gtin`,`p_m_id`,`p_price`,`p_delivery`),
    KEY `p_price` (`p_price`),
    KEY `p_parent` (`p_parent`),
    KEY `site_id` (`site_id`),
    KEY `p_gtin_2` (`p_gtin`),
    KEY `p_type` (`p_type`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 ;

我现在已将查询修改为以下内容：

SELECT p_id, p_m_id, p_prod_label, a_platform, p_link, p_price, m_title, m_link, m_avg_rating 
FROM tgmp_affiliates ga 
JOIN tgmp_prices p 
    ON ga.a_code = p.p_gtin 
        AND ga.a_code != '' 
        AND p.p_price = (
            SELECT MIN(tp.p_price) FROM tgmp_prices tp
                WHERE tp.p_m_id = m.m_id
                AND tp.p_parent = '25573'
    )
JOIN tgmp_merchants m 
    ON m.m_id = p.p_m_id 
WHERE ga.site_id = '34' 
    AND p.site_id = '34' 
    AND ga.a_parent = '25573' 
    AND p_type = 'games' 
    AND m.m_hide = 0 
GROUP BY m.m_id
ORDER BY p.p_price ASC

这给出了正确数量的结果，它们非常接近正确的结果集，但我仍然没有得到每个商家的最低价格。

4

2 回答 2

2

也许 ？：

SELECT p_id,
       p_m_id,
       p_prod_label,
       a_platform,
       p_link,
       p_price,
       m_title,
       m_link,
       m_avg_rating
FROM tgmp_affiliates ga
JOIN tgmp_prices p ON ga.a_code = p.p_gtin
AND ga.a_code != ''
JOIN tgmp_merchants m ON m.m_id = p.p_m_id
WHERE ga.site_id = '34'
  AND p.site_id = '34'
  AND ga.a_parent = '25573'
  AND p_type = 'games'
  AND m.m_hide = 0
  AND p.p_price = (SELECT MIN(p2.p_price) 
                   FROM tgmp_prices p2
                   WHERE p2.p_m_id = m.m_id)
ORDER BY p.p_price ASC
于 2013-03-28T12:17:12.143 回答
1

您使用子查询作为标准，而不是将其添加为额外的记录源。这是一个调整：

SELECT p_id, p_m_id, p_prod_label, a_platform
       , p_link, p_price, m_title, m_link, m_avg_rating, MinPrice
FROM tgmp_affiliates ga 
JOIN tgmp_prices p 
    ON ga.a_code = p.p_gtin 
        AND ga.a_code != ''
JOIN tgmp_merchants m 
    ON m.m_id = p.p_m_id 

JOIN
    (
        SELECT tp.p_m_id as lp_m_id, MIN(tp.p_price) AS MinPrice FROM tgmp_prices tp
            WHERE tp.p_parent = '25573'
            GROUP BY tp.p_m_id
    ) LowestPriceForEachMerchant
    ON m.m_id = LowestPriceForEachMerchant.lp_m_id

WHERE ga.site_id = '34' 
    AND p.site_id = '34' 
    AND ga.a_parent = '25573' 
    AND p_type = 'games' 
    AND m.m_hide = 0 
GROUP BY m.m_id
ORDER BY p.p_price ASC
于 2013-03-28T12:03:18.490 回答