Question

我想获得特定地点的每种产品的价格。这是我到目前为止所做的。

SELECT pl.id AS place_id,
pl.data_name AS place_name,
pp.data_price AS product_price,
pp.date_updated AS price_updated

FROM places AS pl
JOIN products AS pr
ON pl.id = pr.id_place
JOIN products_prices AS pp
WHERE pp.id_product = '30'
GROUP BY pl.id, pp.data_price, pp.date_updated
ORDER BY pp.data_price DESC, pp.date_updated DESC

从上图中可以看出，product_price和price_updated都是一样的。 place_name还会显示3个地方没有ID为30的产品。

以下是它应该是什么样的（最便宜的，最近购买的产品）：

place_id    place_name        product_price    price_updated
       3    ICA Maxi                   4.95    2018-05-16
       1    ICA Supermarket            5.90    2018-05-27
      26    ICA Skutan                 6.50    2018-05-29

这是数据库结构：

CREATE TABLE IF NOT EXISTS `places` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `data_name` tinytext NOT NULL,
  `data_address` text,
  `data_address_city` tinytext NOT NULL,
  `data_coordinates` varchar(50) NOT NULL,
  UNIQUE KEY `id` (`id`)
);

INSERT INTO `places` (`id`, `data_name`, `data_address`, `data_address_city`, `data_coordinates`) VALUES
    (1, 'ICA Supermarket', 'Björkhagsgatan 9', 'Skoghall', '59.324971,13.467291'),
    (2, 'ICA Maxi', 'Bergviks Köpcentrum', 'Karlstad', '59.376563,13.428787'),
    (3, 'ICA Kvantum', 'Bivägen 11', 'HammarÃ¶', '59.343388,13.504583'),
    (4, 'IKEA', 'Bergviksvägen 43', 'Karlstad', '59.379032,13.420646'),
    (5, 'Karlstad Naprapatklinik', 'Västra Torggatan 15', 'Karlstad', '59.381379,13.501683'),
    (9, 'BesÃ¶k i Borgvik AB', '', 'Borgvik', '59.348261,12.954707'),
    (23, 'Mariebergsskogen', '', 'Karlstad', '59.369403,13.486485'),
    (24, 'Happy Price', 'Brehogsvägen 20', 'Tanumshede', '58.723730,11.344768'),
    (25, 'Trekanten KÃ¶k & Bar', 'Parkvägen 2', 'Hamburgsund', '58.552733,11.270998'),
    (26, 'ICA Skutan', 'Strandvägen', 'Hamburgsund', '58.552122,11.270898');



CREATE TABLE IF NOT EXISTS `products` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `id_place` int(11) NOT NULL,
  `data_barcode` text NOT NULL,
  `data_name` text NOT NULL,
  `data_weight` text NOT NULL,
  `data_weight_type` text NOT NULL,
  UNIQUE KEY `id` (`id`)
);

INSERT INTO `products` (`id`, `id_place`, `data_barcode`, `data_name`, `data_weight`, `data_weight_type`) VALUES
    (7, 3, '7311070008494', 'Pågen Lantbröd', '650', 'g'),
    (8, 3, '7310618084808', 'Grumme citronsåpa', '750', 'ml'),
    (9, 3, '7318690079835', 'ICA Basic toalettpapper', '', ''),
    (12, 1, '7318690134640', 'ICA Basic Milk & Caramel', '100', 'g'),
    (18, 3, '7310380512103', 'ICA Home dishmatic refillsvamp', '', ''),
    (19, 3, '7340109200684', 'Plastkasse', '', ''),
    (20, 1, '7310751163903', 'ICA tonfisk filébitar i vatten', '185', 'g'),
    (24, 1, '7310865001818', 'Arla mellanmjölk', '1.5', 'kg'),
    (25, 1, '7318690079712', 'ICA kattsand (klumpbildande, ej parfym)', '6', 'kg'),
    (29, 26, '3068320055008', 'Evian mineralvatten', '500', 'mL'),
    (30, 26, '7318690134640', 'ICA Basic Milk & Caramel', '100', 'g'),
    (33, 2, '0', 'ICA Basic Milk & Caramel', '100', 'g');



CREATE TABLE IF NOT EXISTS `products_prices` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `id_product` int(11) NOT NULL,
  `id_transaction` int(11) NOT NULL,
  `data_price` decimal(10,2) NOT NULL,
  `data_amount` tinytext NOT NULL,
  `data_discount` tinytext,
  `data_discount_amount` tinytext,
  `data_discount_sum` tinytext,
  `data_pant` tinytext,
  `date_updated` date NOT NULL,
  UNIQUE KEY `id` (`id`)
);

INSERT INTO `products_prices` (`id`, `id_product`, `id_transaction`, `data_price`, `data_amount`, `data_discount`, `data_discount_amount`, `data_discount_sum`, `data_pant`, `date_updated`) VALUES
    (1, 1, 907, 18.90, '4', '', '2', '30', NULL, '2018-05-18'),
    (2, 12, 907, 4.90, '4', '', '', '', NULL, '2018-05-18'),
    (5, 4, 904, 18.90, '1', '', '', '', NULL, '2018-05-18'),
    (6, 14, 904, 14.90, '1', '', '', '', NULL, '2018-05-18'),
    (17, 19, 936, 2.00, '1', '', '', '', NULL, '2018-05-21'),
    (18, 21, 947, 23.90, '1', '', '', '', NULL, '2018-05-23'),
    (19, 22, 947, 10.50, '1', '', '', '', NULL, '2018-05-23'),
    (20, 20, 947, 15.90, '1', '', '', '', NULL, '2018-05-23'),
    (21, 13, 947, 49.90, '1', '', '', '', NULL, '2018-05-23'),
    (22, 23, 948, 14.90, '1', '', '', '', NULL, '2018-05-24'),
    (23, 24, 961, 14.90, '1', NULL, NULL, NULL, NULL, '2018-05-27'),
    (24, 12, 961, 5.90, '4', NULL, NULL, NULL, NULL, '2018-05-27'),
    (32, 28, 967, 8.50, '2', NULL, NULL, NULL, NULL, '2018-05-28'),
    (33, 29, 972, 12.90, '1', NULL, NULL, NULL, '1', '2018-05-29'),
    (34, 30, 973, 6.50, '2', NULL, NULL, NULL, NULL, '2018-05-29'),
    (35, 31, 976, 10.00, '1', NULL, NULL, NULL, NULL, '2018-05-30'),
    (36, 32, 976, 10.00, '1', NULL, NULL, NULL, NULL, '2018-05-30');

Answer 1

试试这个：

SELECT PL.id AS place_id,
PL.data_name AS place_name,
PP.data_price AS product_price,
PP.date_updated AS price_updated
FROM products_prices PP
JOIN products PR
    ON PR.id = PP.id_product
JOIN places PL
    ON PL.id = PR.id_place
WHERE PR.id = '30'

Answer 2

正如我对您的请求的评论中所述：您忘记了将ON表与其他两个表相关联的products_prices子句。

MariaDB将您的内部联接转换为交叉联接，而不是引发错误。这给你的是：选择产品30的所有价格与所有地方相结合乘以其中的产品数量，而不是仅仅与产品的位置相结合。

顺便说一下：我将表products放在FROM子句中，因为这是基础（你想要产品30）。然后加入产品的价格和产品的位置。

没有理由对您的数据进行分组，因为您只想列出价格。你没有聚合任何东西。所以你得到：

SELECT 
  pl.id AS place_id,
  pl.data_name AS place_name,
  pp.data_price AS product_price,
  pp.date_updated AS price_updated
FROM products AS pr
JOIN products_prices AS pp ON pp.id_product = pr.id
JOIN places pl ON pl.id = pr.id_place
WHERE pr.id = 30
ORDER BY pp.data_price DESC, pp.date_updated DESC;

获取特定ID

2 个答案: