Question

我有一个表，其中包含具有其属性（例如DepId和FieldId）的Lessons。我也有两个表格，分别是关于课程部门和课程字段。我需要根据DepId和FieldId计算课程每周的上课时间百分比。我的查询如下：

  Select a.FieldName, b.DepName, sum(LessonWeeklyTime), ((sum(LessonWeeklyTime))*100)/(select LessonDep, sum(LessonWeeklyTime) 
    From Lessons 
Group By LessonDep) 
    from Lessons l, Departments b, Fields a 
   Where l.LessonDep=b.DepId 
     And l.LessonField=a.FieldId 
Group By b.DepName,a.FieldName

但是我遇到了错误：

第16层，状态1，第2行，消息116 如果未使用EXISTS引入子查询，则只能在选择列表中指定一个表达式。

感谢帮助。

Answer 1

从不在FROM子句中使用逗号。始终使用正确的，明确的标准 JOIN语法。毕竟是21世纪。

您应该使用窗口功能执行此操作

select f.FieldName, d.DepName, sum(LessonWeeklyTime), 
       (sum(LessonWeeklyTime) * 100.0 / 
        sum(sum(LessonWeeklyTime)) over (partition by d.depName)
from Lessons l join
     Departments d
     on l.LessonDep = d.DepId join
     Fields f
     on l.LessonField = f.FieldId 
Group By d.DepName, f.FieldName

Answer 2

错误消息指出，子查询中可能只有一列。尝试这种方式：

Select a.FieldName, b.DepName, sum(LessonWeeklyTime), ((sum(LessonWeeklyTime))*100)/(select sum(LessonWeeklyTime) 
    From Lessons 
Group By LessonDep) 
    from Lessons l, Departments b, Fields a 
   Where l.LessonDep=b.DepId 
     And l.LessonField=a.FieldId 
Group By b.DepName,a.FieldName

Answer 3

检查此：

Select a.FieldName, b.DepName, sum(LessonWeeklyTime), ((sum(LessonWeeklyTime))*100)/ sum(c.LessonWeeklyTime)
        from Lessons l, Departments b, Fields a ,(select LessonDep, sum(LessonWeeklyTime) LessonWeeklyTime 
        From Lessons 
Group By LessonDep) c
       Where l.LessonDep=b.DepId 
         And l.LessonField=a.FieldId 
         And l.LessonDep=c.LessonDep
Group By b.DepName,a.FieldName

Answer 4

通过必要的代码从1个表中获取时间，并使用窗口函数表示百分比。它通过ID（而不是描述）进行分组/计算，以提高性能并减少由于标签/标签无效而出现错误的可能性：

WITH CTE AS( SELECT LESSONDEP, LESSONFIELD, SUM(LESSONWEEKLYTIME) AS [TIME] 
FROM [LESSONS] 
GROUP BY LESSONDEP, LESSONFIELD) 
SELECT F.FIELDNAME, D.DEPNAME, L.[TIME], (L.[TIME]*100.0) / (SUM(L.[TIME]) OVER (PARTITION BY L.LESSONDEP) AS [PERCENTAGE] 
FROM CTE L 
INNER JOIN DEPARTMENTS D ON L.LESSONDEP = D.DEPID 
INNER JOIN FIELDS F ON L.LESSONFIELD = F.FIELDID

使用“分组依据”子查询计算字段

4 个答案: