开课表数据如下,其中OpenCno为选课编号,Cno为课程编号,Tno为教师编号,ClassNo班级编号, 计算每个
A、SELECT Cno AS 班级号,选课人数= CASE WHEN COUNT(*)=1 THEN ’一位同学选修’ WHEN COUNT(*)=2 THEN ’两位同学选修’ WHEN COUNT(*)=3 THEN ’三位同学选修’ END FROM 开课表 GROUP BY ClassNo
B、SELECT Cno AS 班级号,选课人数= CASE WHEN COUNT(*)=1 THEN ’一位同学选修’ WHEN COUNT(*)=2 THEN ’两位同学选修’ WHEN COUNT(*)=3 THEN ’三位同学选修’ END FROM 开课表 GROUP BY Cno
C、SELECT ClassNo AS 班级号,选课人数= CASE WHEN COUNT(*)=1 THEN ’一位同学选修’ WHEN COUNT(*)=2 THEN ’两位同学选修’ WHEN COUNT(*)=3 THEN ’三位同学选修’ END FROM 开课表 GROUP BY Cno
D、SELECT ClassNo AS 班级号,选课人数= CASE WHEN COUNT(*)=1 THEN ’一位同学选修’ WHEN COUNT(*)=2 THEN ’两位同学选修’ WHEN COUNT(*)=3 THEN ’三位同学选修’ END FROM 开课表 GROUP BY ClassNo