mysql - 获取每个月的交易余额

Question

我得到了一个包含事务的 2 列表，其中存储了更改时间 (unix_time) 和更改值。

create table transactions (    
  changed int(11),
  points int(11)
);

insert into transactions values (UNIX_TIMESTAMP('2014-03-27 03:00:00'), +100);
insert into transactions values (UNIX_TIMESTAMP('2014-05-02 03:00:00'), +100);
insert into transactions values (UNIX_TIMESTAMP('2015-01-01 03:00:00'), -100);
insert into transactions values (UNIX_TIMESTAMP('2015-05-01 03:00:00'), +150);

要获得当前余额，您需要对所有值求和，而要获得过去的余额，如果该值的更改时间少于请求的时间，则需要求和，如下所示:

select 
    sum(case when changed < unix_timestamp('2013-12-01') then 
            points 
        else 
            0 
        end) as cash_balance_2013_11,
...

因此每个月都需要有一个单独的 SQL 代码。我想要 SQL 代码来为我提供所有月份的余额。 (例如从固定日期到现在)

编辑:

HERE IS SQL FIDDLE

Answer 1

您可以只分组依据和按月份排序吗？

更新:要获得运行总计，您必须将各个月份加入到一组按月总计中，匹配“小于或等于”:-

select
     m.single_month
   , sum(month_of_change.total_points)  as running total_by_month
from
(
   select 
        sum(points) as total_points
      , month_of_change
   from 
   (
   select 
        points
      , MONTH(FROM_UNIXTIME(t.time_of_change)) as month_of_change -- assumes unix_time
   from mytable t
   ) x
   group by month_of_change 
) monthly_totals
inner join
(
   select distinct MONTH(FROM_UNIXTIME(t.time_of_change)) as single_month
) m
on monthly_totals.month_of_change <= m.single_month
group by m.single_month

(注意:未测试)