mysql - 为什么 mysql sum 在 mysql 查看表中不起作用？

Question

我使用以下查询从 mysql View 表中获取总分

Select regd, date, subject, (t_scored+w_scored+f_scored+cce_scored) as Total
from
exam_view
where regd='3'
group by subject

在总计列中，我只得到 NULL，其中每个评分字段都有字段值。请问有人可以帮助我吗？

Answer 1

使用内联查询获取单独的总和，使用外部查询将总和相加

SELECT regd, date, subject, SUM(t_scored+w_scored+f_scored+cce_scored) AS total
FROM
(
SELECT regd, date, subject, SUM(t_scored) as t_scored, SUM(w_scored) as w_scored, SUM(f_scored) AS f_scored, SUM(cce_scored) AS cce_scored
FROM
exam_view
WHERE regd='3'
) AS temp
GROUP BY subject