Question

我正在创建一个临时表，它目前为今天和昨天提取值。临时表如下所示：

|DateTime                |company 1 |company 2 |
+------------------------+----------------------+
|2013-10-03 14:40:00     | 182475   |  110271  |
|2013-10-02 14:10:00     | 182086   |  110261  |

我需要做的是选择今天的值，以及今天和昨天之间的差异。根据以上数据，输出结果如下：

Company 1   | Company 1 difference | Company 2|  Company 2 difference
+-----------+----------------------+----------+--------------------------
182475      |         389          | 110271   |          10

我无法弄清楚如何指定要从哪一行中减去哪一行，因为没有自动增量字段，而且DateTime字段每天会略有不同。

感谢您的帮助！

Answer 1

SELECT today.DateTime as DateTime
  , today.Company1, today.Company1 - COALESCE(yesterday.Company1,0) AS Company1Diff
  , today.Company2, today.Company2 - COALESCE(yesterday.Company2,0) AS Company2Diff
FROM tbl AS today
LEFT JOIN tbl AS yesterday
ON DATEDIFF(today.DateTime, yesterday.DateTime) = 1
ORDER BY today.DateTime ASC

MySQL - 从第1行减去第2行，其中列是相同的

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