Question

我正在使用库存数据，每分钟告诉我当前的库存水平并将其存储在数据库中。

我想找到item_count下降为0的每个实例，将该行带有时间戳，然后将其加入到item_count超过0的下一行。这将告诉我该产品缺货多长时间。

我想出了以下内容，但它没有返回任何内容。

SELECT `inventories`.* from `inventories` inner join 
    (SELECT id, item_count, pusher_id, created_at as in_stock_at
                FROM inventories
                GROUP BY pusher_id) inv2 
ON `inventories`.`created_at` < `inv2`.`in_stock_at` 
    AND `inv2`.`item_count` > `inventories`.`item_count` 
    AND `inventories`.`pusher_id` = `inv2`.`pusher_id` 
WHERE `inventories`.`item_count` <= 0 
    AND `inventories`.`product_id`=9

结构::

CREATE TABLE IF NOT EXISTS `inventories` (
  `id` int(10) unsigned NOT NULL,
  `client_id` int(10) unsigned NOT NULL,
  `pusher_id` int(10) unsigned NOT NULL,
  `product_id` int(10) unsigned NOT NULL,
  `reader_id` int(10) unsigned NOT NULL,
  `tags_blocked` double(6,2) NOT NULL,
  `item_count` double(6,2) NOT NULL,
  `active` tinyint(1) NOT NULL DEFAULT '1',
  `created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `deleted_at` timestamp NULL DEFAULT NULL
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=2881 ;

数据::

INSERT INTO `inventories` (`id`, `client_id`, `pusher_id`, `product_id`, `reader_id`, `tags_blocked`, `item_count`, `active`, `created_at`, `updated_at`, `deleted_at`) VALUES
    (1, 1, 1, 9, 1, 0.00, 0.00, 1, '2015-10-22 04:45:47', '2015-10-23 04:45:47', NULL),
    (2, 1, 1, 9, 1, 0.00, 0.00, 1, '2015-10-22 04:55:47', '2015-10-23 04:45:47', NULL),
    (3, 1, 1, 9, 1, 0.00, 0.00, 1, '2015-10-22 05:05:47', '2015-10-23 04:45:47', NULL),
    ...
    (10, 1, 1, 9, 1, 0.00, 0.00, 1, '2015-10-22 06:15:47', '2015-10-23 04:45:47', NULL),
    (11, 1, 1, 9, 1, 10.00, 10.00, 1, '2015-10-22 06:25:47', '2015-10-23 04:45:47', NULL),
    (12, 1, 1, 9, 1, 9.00, 9.00, 1, '2015-10-22 06:35:47', '2015-10-23 04:45:47', NULL),
    (13, 1, 1, 9, 1, 8.00, 8.00, 1, '2015-10-22 06:45:47', '2015-10-23 04:45:47', NULL),

期望结果::

根据上面的数据，我想加入ID为1的行和ID为11的行。 1.在表中搜索item_count = 0的第一行，找到具有item_count＆gt;的行（具有相同的product_id和pusher_id）。 0和created_at＆gt; firstRow.created_at。并将他们加在一起。然后，找到此事件的下一个实例。

我希望澄清这个问题。

Answer 1

转换为SQL并不难，但性能可能不好。这将为您提供产品重新库存时的时间戳：

SELECT inv.*,
 ( SELECT MIN(`inv2`.`in_stock_at`)
   FROM inventories AS inv2
   WHERE inv2.`product_id` = inv.`product_id`   -- same product
     AND inv2.`pusher_id` = `inv`.`pusher_id`   -- same pusher
     AND `inv2`.`created_at` > inv.`created_at` -- later timestamp
     AND `inv2`.`item_count` > 0                -- in stock
 ) AS inStockAgain_at
from `inventories` AS inv
WHERE inv.`item_count` <= 0   -- out of stock
 -- AND inv.`product_id`=9

编辑：

删除零库存的连续行更复杂：

SELECT inv.*, dt.inStockAgain_at
FROM inventories AS inv
JOIN
 ( 
   SELECT product_id, pusher_id, 
      MIN(created_at) AS min_created_at,
     inStockAgain_at
   FROM
    (
      SELECT product_id, pusher_id, created_at,
       ( SELECT MIN(inv2.created_at)
         FROM inventories AS inv2
         WHERE inv2.product_id = inv.product_id -- same product
           AND inv2.pusher_id = inv.pusher_id   -- same pusher
           AND inv2.created_at > inv.created_at -- later timestamp
           AND inv2.item_count > 0              -- in stock
       ) AS inStockAgain_at
      FROM inventories AS inv
      WHERE inv.item_count <= 0  
    ) AS dt
   GROUP BY product_id, pusher_id, inStockAgain_at
 ) AS dt
ON inv.product_id = dt.product_id
AND inv.pusher_id = dt.pusher_id 
AND inv.created_at = dt.min_created_at

请参阅fiddle

SQL根据时间戳和库存级别

1 个答案: