Question

这是我的表格

CREATE TABLE Course(Cno CHAR(6), Cname NVARCHAR(20) NOT NULL,PRIMARY KEY(Cno))
CREATE TABLE SC(Sno CHAR(7) NOT NULL,Cno CHAR(6) NOT NULL,Grade TINYINT,
    PRIMARY KEY(Sno, Cno),
    FOREIGN KEY(Sno) REFERENCES Student(Sno),
    FOREIGN KEY(Cno) REFERENCES Course(Cno)
)

表课程

Cno    Cname    
------------
C001   Math
C002   CS
C003   Database

表格SC

Sno    Cno    Grade
-------------------
1      C001   80
2      C002   90
2      C003   70
3      C002   60

...想要：

Cno    Cname    Number
-----------------------
C002   CS       2
C001   Math     1
C003   Database 1

此代码已经完成

select top 3 with ties Course.Cno, Course.Cname, count(SC.Cno) AS Number 
from Course left join SC
  on Course.Cno = SC.Cno
  group by Course.Cno, Cname, Semester
  order by count(SC.Cno) desc

但如果我使用＆＃34;由Course.Cno＆＃34;组合，则无法工作..

为什么我必须添加＆＃34; Cname，Semester＆＃34;？

我试过mysql working..but sql server 2012 not。

Answer 1

使用子查询来获取计数：

select Cno, Cname, (select count(*) from sc where c.cno = sc.cno) as cnt
from Course as c
order by cnt

SQL Group By Multiple columns＆amp;多个表

1 个答案: