在 MySQL 中创建累积总和列
我有一张看起来像这样的表格:
I have a table that looks like this:
id count
1 100
2 50
3 10
我想添加一个名为cumulative_sum的新列，因此该表将如下所示:
I want to add a new column called cumulative_sum, so the table would look like this:
id count cumulative_sum
1 100 100
2 50 150
3 10 160
是否有可以轻松完成此操作的 MySQL 更新语句?实现这一目标的最佳方法是什么?
Is there a MySQL update statement that can do this easily? What's the best way to accomplish this?
推荐答案
如果性能有问题，您可以使用 MySQL 变量:
If performance is an issue, you could use a MySQL variable:
set @csum := 0;
update YourTable
set cumulative_sum = (@csum := @csum + count)
order by id;
或者，您可以删除 cumulative_sum 列并在每个查询中计算它:
Alternatively, you could remove the cumulative_sum column and calculate it on each query:
set @csum := 0;
select id, count, (@csum := @csum + count) as cumulative_sum
from YourTable
order by id;
这以运行方式计算运行总和:)
This calculates the running sum in a running way :)
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