amounts, MySQL - rextester

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#MySQL 5.7.12
#please drop objects you've created at the end of the script 
#or check for their existance before creating
#'\\' is a delimiter

select version() as 'mysql version'
\\
CREATE TABLE my_table
(
  rdate date,
  ramaount int
);
\\
INSERT INTO
  my_table (rdate, ramaount)
VALUES
  ('2015-01-01',  375),
  ('2015-03-01',  950),
  ('2015-05-01', 1730),
  ('2015-06-01', 1200),
  ('2015-07-01', 6000),
  ('2015-08-01',  300),
  ('2015-09-01',  200),
  ('2015-10-01',  180),
  ('2015-12-01', 1200)
;
\\
# 1 column
 select month(rdate),
(SELECT SUM(ramaount) 
 FROM my_table 
 WHERE (month(rdate) <(month(a.rdate)))
 and year(rdate)=2015
) as total_previous
FROM my_table a
where year(rdate)=2015
group by month(rdate)
order by year(rdate),month(rdate);
\\
# 2 column
select
month(rdate) as month_2015,
sum(ramaount)
from     my_table
where    year(rdate) in (2015)
group by   month(rdate);
\\
# 3h colum
SELECT month(rdate),
(SELECT SUM(ramaount) 
 FROM my_table 
 WHERE (month(rdate) >(month(a.rdate)))
 and year(rdate)=2015
) as total_next
FROM my_table a
where year(rdate)=2015
group by month(rdate);
\\

SELECT
  month_2015,
  NULLIF(past_amount - this_amount, 0) AS past_amount,
  this_amount,
  NULLIF(future_amount - this_amount, 0) AS future_amount
FROM
  (
    SELECT
      month_2015,
      this_amount,
      past_amount,
      @future_amount := @future_amount + this_amount AS future_amount
    FROM
      (SELECT @future_amount := 0) AS x,
      (
        SELECT
          month_2015,
          this_amount,
          @past_amount := @past_amount + this_amount AS past_amount
        FROM
          (SELECT @past_amount := 0) AS x,
          (
            SELECT
              MONTH(rdate) AS month_2015,
              SUM(ramaount) AS this_amount
            FROM
              my_table
            GROUP BY
              MONTH(rdate)
          ) AS sub
        ORDER BY
          month_2015 ASC
      ) AS sub
    ORDER BY
      month_2015 DESC
  ) AS sub
ORDER BY
  month_2015 ASC
;
\\

SELECT
  month_2015,
  @past_amount := @past_amount + @this_amount AS past_amount,
  @this_amount := this_amount AS this_amount, 
  total_amount - @past_amount - @this_amount AS future_amount
FROM
          (SELECT @past_amount := 0, @this_amount := 0) AS x,
  
          ( SELECT SUM(ramaount) AS total_amount
            FROM my_table
            WHERE rdate >= DATE '2015-01-01'
              AND rdate < DATE '2016-01-01'
          ) t,
          
          (
            SELECT
              MONTH(rdate) AS month_2015,
              SUM(ramaount) AS this_amount
            FROM
              my_table
            WHERE
                  rdate >= DATE '2015-01-01'
              AND rdate < DATE '2016-01-01'
            GROUP BY
              MONTH(rdate)
          ) AS sub 
;
\\

DROP TABLE my_table;
\\


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