一行的总和（两列的平均值）和相同的行（另一列的值）

Question

我已经写了一个查询，但它显示错误。我希望得到mid_1_english和mid_2_english的AVG，然后想要将{AVGG添加到semester_final_english。

select s_roll_no, s_f_name, s_l_name, s_class, 
           SUM(mid_1_english + mid_2_english)/2 as mid_english, 
           SUM(mid_1_mathematics + mid_2_mathematics)/2 as mid_mathematics, 
           SUM(mid_english + semester_final_english) as total_english, 
           SUM(mid_mathematics + semester_final_mathematics) as total_mathematics 
from elaborate_result 
group by s_f_name, s_l_name;
LIMIT 0, 50000 

  

错误代码：1054。未知栏＆＃39; mid_english＆＃39;在＆＃39;字段列表＆＃39; 0.000   秒

Answer 1

当你做这样的事情时

    Select SUM(mid_1_english + mid_2_english)/2 as mid_english 

它不会创建新列mid_english。因此，您不能在同一查询中将其用作列。

所以你需要的东西可能看起来像这样

    select s_roll_no, s_f_name, s_l_name, s_class, 
       SUM(mid_1_english + mid_2_english)/2 as mid_english, 
       SUM(mid_1_mathematics + mid_2_mathematics)/2 as mid_mathematics, 
       SUM((mid_1_english + mid_2_english)/2 + semester_final_english) as 
     total_english, 
      SUM((mid_1_mathematics + mid_2_mathematics)/2 + 
     semester_final_mathematics) as total_mathematics 
    from elaborate_result 
  group by s_f_name, s_l_name;
 LIMIT 0, 50000