mysql - SQL根据时间戳和库存水平连接同一张表

Question

我正在处理每分钟告诉我当前库存水平并将其存储在数据库中的库存数据。

我想找到 item_count 下降到 0 的每个实例，获取带有时间戳的那一行，然后将它连接到 item_count 上升到 0 以上的下一行。然后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),

期望的结果::

鉴于上述数据，我想连接 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 item_count > 0 且 created_at > firstRow.created_at 的行(具有相同的 product_id 和 pusher_id)。并加入他们。然后，找到这种情况的下一个实例。

我希望这能澄清问题。

Answer 1

转换成 SQL 并不难，但性能可能很差。这将为您提供产品重新入库的时间戳:

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:

删除库存为零的连续行更加复杂:

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 

参见 fiddle