在MySQL中运行多个类别的求和
我有一张表格在MySQL中运行多个类别的求和,mysql,sql,cumulative-sum,Mysql,Sql,Cumulative Sum,我有一张表格 Category Time Qty A 1 20 B 2 3 A 3 43 A 4 20 B 5 25 我需要在MySQL中按类别计算一个运行总数。结果如下所示: Category Time Qty Ca
Category Time Qty
A 1 20
B 2 3
A 3 43
A 4 20
B 5 25
我需要在MySQL中按类别计算一个运行总数。结果如下所示:
Category Time Qty Cat.Total
A 1 20 20
B 2 3 3
A 3 43 63
A 4 20 83
B 5 25 28
你知道我如何在MySQL中高效地实现这一点吗?我已经搜索了很多地方,但我能找到的只是关于如何在MySQL中插入一个运行总数的信息。我想知道是否有任何方法可以使用GROUP BY或类似的构造来实现这一点。您可以在子查询中计算总和:
select Category
, Time
, Qty
, (
select sum(Qty)
from YourTable t2
where t1.Category = t2.Category
and t1.Time >= t2.Time
) as CatTotal
from YourTable t1
select Category
, Time
, Qty
, CatTotal
from (
select Category
, Time
, Qty
, @sum := if(@cat = Category,@sum,0) + Qty as CatTotal
, @cat := Category
from YourTable
cross join
(select @cat := '', @sum := 0) as InitVarsAlias
order by
Category
, Time
) as SubQueryAlias
order by
Time
以可读性换取速度,您可以使用MySQL变量来保存运行总和:
select Category
, Time
, Qty
, @sum := if(@cat = Category,@sum,0) + Qty as CatTotal
, @cat := Category
from YourTable
cross join
(select @cat := '', @sum := 0) as InitVarsAlias
order by
Category
, Time
需要订购才能使该结构正常工作;如果需要不同的顺序,请将查询包装在子查询中:
select Category
, Time
, Qty
, (
select sum(Qty)
from YourTable t2
where t1.Category = t2.Category
and t1.Time >= t2.Time
) as CatTotal
from YourTable t1
select Category
, Time
, Qty
, CatTotal
from (
select Category
, Time
, Qty
, @sum := if(@cat = Category,@sum,0) + Qty as CatTotal
, @cat := Category
from YourTable
cross join
(select @cat := '', @sum := 0) as InitVarsAlias
order by
Category
, Time
) as SubQueryAlias
order by
Time
它必须是一个连续的总数,还是可以一次计算出最终的总数?我需要这个@fredley的连续总数,你知道怎么做吗?假设我有和他一样的表格,这个方案的效果如何,没有考虑时间栏。它确实在一定程度上起作用。。。但是,随着时间的推移,计算出的总数是不起作用的,仅就类别而言是不起作用的我仍在研究解决方案。