MySQL - 選擇一年中總和的最大值

Question

我有這樣的表：

  v   | day | month | year
  1      1     1      1950
  2      2     1      1950
  3      3     1      1950
  1      1     2      1950
  1      1     2      1951
  2      1     2      1952

我已使用此查詢來選擇 MIN

SELECT SUM(v) AS sum_val, year, month
FROM `d`
GROUP BY year, month

這將導致

sum_val | year | month  
  6       1950     1
  1       1950     2
  1       1951     2 
  2       1952     2

如何選擇按月分組的指定年份的 sum_val 最大值？ 我試過了

SELECT (MAX(f.sum_val)) AS max_sum, f.year, f.month
FROM (
    SELECT SUM(v) AS sum_val, year, month
    FROM `d`
    GROUP BY year, month
) AS f
GROUP BY month

但這錯誤地將年份分配給價值

max_sum | year | month  
   6      1950    1
   2      1950    2   <--- should be 1952

SqlFiddle： http ://sqlfiddle.com/#!9/ab23b4/6/0

Answer 1

您可以在 join 中使用一些基於 sum_val 的子查詢 baset

select t2.sum_val, t2.year, t2.month 
from (
    SELECT SUM(v) AS sum_val, year, month
    FROM `d`
    GROUP BY year, month
) t2 
INNER JOIN (
    select max(sum_val) max_val, year
    from (
        SELECT SUM(v) AS sum_val, year, month
        FROM `d`
        GROUP BY year, month
    )  t  
    group by year 
) t3  on t3.max_val = t2.sum_val    and t3.year  = t2.year

請注意，如果您有兩行與 max val 匹配，則查詢將返回兩行