Question

我需要按行计算课程数。这意味着将课程后的大学名称添加到一行

College_name    course_name1   course_name2    course_name3    course_name4 
----------------------------------------------------------------------------
ABC College     computer       bca             cdb  
xbc college     acvb           bca             ads             abc
xdb college     cgd            ghdg           
vvv college     anb            abd             bca

我在SQL中需要这样的结果格式。我需要计算课程数：

College_name      course_count 
------------------------------
ABC College          3
xbc college          4
xdb college          2     
vvv college          3

Answer 1

您可以使用union all：

select College_name, count(Course) as course_count 
from (select College_name, course_name1 as Course
      from table 
      union all
      select College_name, course_name2 
      from table 
      . . .
     ) t
group by College_name;

Answer 2

您的数据结构非常差。您应该有一个CollegeClasses表，每个学院和每个班级一行。那么这将是简单的聚合。

相反，您可以做一个大的表情来添加内容：

select college_name,
       ( (case when course_name1 is not null then 1 else 0 end) +
         (case when course_name2 is not null then 1 else 0 end) +
         (case when course_name3 is not null then 1 else 0 end) +
         (case when course_name4 is not null then 1 else 0 end)
       ) as num_courses
from t;

Answer 3

您可以结合使用取消透视和分组：

SELECT
  College_name,
  COUNT(course_name) AS course_count
FROM
(
  SELECT
    College_name,
    course_name
  FROM
    table AS t
  UNPIVOT
  (
    course_name for courses in (course_name1, course_name2, course_name3, course_name4)
  ) AS unpiv
) AS d
GROUP BY
  College_name

Answer 4

如果您使用的是UNPIVOT，则可以使用sql-server

SELECT College_name, COUNT(*) course_count 
FROM MyTable 
UNPIVOT( V FOR C IN (course_name1, course_name2, course_name3, course_name4)) UNPVT
GROUP BY College_name

Answer 5

您将通过以下代码获取课程计数，如果适合您，请标记正确答案

select (course_name1 + course_name2 + course_name3 + course_name4 ) as course_count  from (select case when course_name1 is not null then 1 else 0 end as course_name1, case when
 course_name2 is not null then 1 else 0 end as course_name2,
 case when course_name3 is not null then 1 else 0 end as course_name3,case when 
 course_name4 is not null then 1 else 0 end as course_name4
 from desktopschduleremark ) as tst

计算SQL中单列之后的行

5 个答案: