本文介绍了计算上一行值的增加/减少百分比的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有一个看起来像这样的表:
I have a table that looks something like this:
|date_start | date_end |amount |
+------------+-------------+-------+
|2015-02-23 | 2015-03-01 |50 |
|2015-03-02 | 2015-03-08 |50 |
|2015-03-09 | 2015-03-15 |100 |
|2015-03-16 | 2015-03-22 |800 |
|2015-03-23 | 2015-03-29 |50 |
，我想算出前一天以来列amount的增加/减少百分比.例如，结果将是这样，
and I'd like to work out the percent increase/decrease for column amount, from the previous date. For example the result would be something like this,
|date_start | date_end |amount | perc_change |
+------------+-------------+-------+-------------+
|2015-02-23 | 2015-03-01 |50 |
|2015-03-02 | 2015-03-08 |50 | 0
|2015-03-09 | 2015-03-15 |100 | 50
|2015-03-16 | 2015-03-22 |800 | 700
|2015-03-23 | 2015-03-29 |50 | -750
我已经搜寻并绞尽脑汁了几天.通常，我只是使用服务器端代码来完成此操作，但是现在我需要将其全部包含在查询中.
I've searched and racked my brain for a couple of days now. Usually, I simply do this using server side code but now I need to contain it all within the query.
推荐答案
尝试一下:
SELECT t.*,
amount - (SELECT amount FROM transactions prev WHERE prev.date_end < t.date_start ORDER BY date_start DESC LIMIT 1) AS changes
FROM transactions t
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