(1) select a1.课程号,a1.课程名,count(*) as 选课人数 from 课程 a1,选课 a2where a1.课程号=a2.课程号group by a1.课程号,a1.课程名(2) select 选课.学生号,学生.姓名,count(选课.学生号) AS 选课数from 选课 ,学生 where 选课.学生号=学生.学生号 group by 选课.学生号 ,学生.姓名 having count(课程号)=1;(3) select 选课.学生号,学生.姓名,count(选课.学生号) AS 选课数from 选课 ,学生 where 选课.学生号=学生.学生号 group by 选课.学生号 ,学... |