mysql - 如何按年度计算员工总数和员工总数

Question

这是我的员工表

empid   name     Date_of_joining
  1      dilip       2010-01-30
  2      suresh      2001-03-01
  3      ramesh     2003-01-01

我想按员工入职日期获取员工总数和员工总数

预期输出

   year    new joining    total employees
   2001          10                10
   2002          12                22
   2003          15                27

查询

 select YEAR(`DATE_OF_JOINING`) as 'year', COUNT(*) as 'count1',sum(count(*)) from employee 

 GROUP BY YEAR(`DATE_OF_JOINING`)

Answer 1

您需要一个使用用户定义变量的运行总计。

您需要一个派生表，因为运行总计不适用于 group by 语句

SET @SUM = 0;
SELECT
  YEAR,
  NoOfEmployee AS newJoining,
  (@SUM := @SUM + NoOfEmployee) AS totalJoining
FROM (
    SELECT
      YEAR(Date_of_joining) AS YEAR,
      COUNT(*) AS NoOfEmployee
    FROM
      employees
    GROUP BY
      YEAR(Date_of_joining)
  ) O

这里是sample