mysql - 在mysql中将初始总和设置为零

Question

我有一个查询可以满足我的需要，但是因为图表的 joomla 插件不接受初始 SET 值为零，我需要一种方法将这个查询转换为 View ，或者至少执行不使用 SET 的算术函数。

基本上，此查询会为每个月显示一列员工总数，加上上个月的员工数并减去离开的员工数。

SELECT
  CONCAT(q1.d,'-',LPAD(q1.m,2,0)) AS Periodo,
q1.c AS `<font color="blue">Assunzioni</font>`,
q1.l AS `<font color="red">Licenziamenti</font>`
FROM
 (SELECT
   YEAR(calendar.datefield) AS d,
   month(calendar.datefield) AS m,
   SUM(statistica_assunti_n.assunzioni) AS c,
   SUM(statistica_licenziati_n.licenziamenti) AS l
FROM  calendar
INNER JOIN statistica_assunti_n
ON calendar.datefield = statistica_assunti_n.data_assunzioni
INNER JOIN statistica_licenziati_n
ON calendar.datefield = statistica_licenziati_n.data_licenziamenti
WHERE YEAR(datefield) ={$REQUEST:chartYearStart|empty:'2011'} 
AND datefield       <= DATE(NOW())
GROUP  BY d, m
ORDER  BY d, m) AS q1 

如有任何帮助，我们将不胜感激。

Answer 1

插件的管理员给了我解决方案，(SELECT @runtot := 0) AS zero:

SELECT
    CONCAT(q1.d,'-',LPAD(q1.m,2,0)) AS Periodo,
   (@runtot := @runtot + q1.c - q1.l) AS `N. dipendenti`
FROM
   (SELECT
       YEAR(calendar.datefield) AS d,
       month(calendar.datefield) AS m,
       SUM(statistica_assunti_n.assunzioni) AS c,
       SUM(statistica_licenziati_n.licenziamenti) AS l
    FROM  calendar
    INNER JOIN statistica_assunti_n
    ON calendar.datefield = statistica_assunti_n.data_assunzioni
  INNER JOIN statistica_licenziati_n
    ON calendar.datefield = statistica_licenziati_n.data_licenziamenti
WHERE YEAR(datefield) = {$REQUEST:chartYearStart|empty:'2011'} AND datefield <= DATE(NOW())
    GROUP  BY d, m
    ORDER  BY d, m) AS q1, (SELECT @runtot := 0) AS zero