mysql - 查询中的累积函数不会分组

Question

我正在尝试重置每种 Insurance_status 的累积计数。现在我的代码返回了累积计数，但当 Insurance_status 更改时不会重新开始。如何将查询设置为分组依据或重置变量以获得我想要的查询。

我尝试在代码中的最后一个 order by 之前添加 group by，但没有成功。

SELECT t.insurance_status, t.day, t.vendor_count,
       @running_total:=@running_total + t.vendor_count AS cumulative_sum
FROM (SELECT insurance_status,
             DATE_FORMAT(date, '%Y %m') as day,
             count(insurance_status) as vendor_count
      FROM vendor_report_jll
      WHERE project_id in (100, 92, 45, 91, 86, 87, 88, 40, 101, 90, 98)
      GROUP BY insurance_status,day
     ) t JOIN
     (SELECT @running_total := 0) AS t2
ORDER BY  t.insurance_status;

Answer 1

您需要另一个变量来记住保险状态:

SELECT t.insurance_status, t.day, t.vendor_count,
       (@sum := if(@is = t.insurance_status, @sum + t.vendor_count,
                   if(@is := t.insurance_status, t.vendor_count, t.vendor_count
                     )
                  )
       ) AS cumulative_sum
FROM (SELECT insurance_status,
             DATE_FORMAT(date, '%Y %m') as day,
             count(insurance_status) as vendor_count
      FROM vendor_report_jll
      WHERE project_id in (100, 92, 45, 91, 86, 87, 88, 40, 101, 90, 98)
      GROUP BY insurance_status, day
      ORDER BY insurance_status, day  -- just being explicit
     ) t CROSS JOIN
     (SELECT @sum := 0, @is := -1) params;

您需要在一条语句中完成所有分配。这是由于 MySQL 的规则所致 - 它不保证 SELECT 中表达式求值的顺序，因此您不能在一个表达式中分配变量并在另一个表达式中使用它们。