SQL查詢GROUP BY

Question

我有以下的記錄和值：

create table student (
    LastName  varchar(40), 
    FirstName  varchar(40), 
    SID   number(5), 
    SSN   number(9), 
    Career  varchar(4), 
    Program  varchar(10), 
    City   varchar(40), 
    Started  number(4), 

    primary key (SID), 
    unique(SSN) 
); 

create table enrolled (
    StudentID  number(5), 
    CourseID  number(4), 
    Quarter  varchar(6), 
    Year   number(4), 

    primary key (StudentID, CourseID), 
    foreign key (StudentID) references student(SID), 
    foreign key (CourseID) references course(CID) 
); 

insert into student 
    values ('Brennigan', 'Marcus', 90421, 987654321, 'UGRD', 'COMP-GPH', 'Evanston', 2001); 
insert into student 
    values ('Patel', 'Deepa', 14662, null, 'GRD', 'COMP-SCI', 'Evanston', 2003); 
insert into student 
    values ('Snowdon', 'Jonathan', 08871, 123123123, 'GRD', 'INFO-SYS', 'Springfield', 2005); 
insert into student 
    values ('Starck', 'Jason', 19992, 789789789, 'UGRD', 'INFO-SYS', 'Springfield', 2003); 
insert into student 
    values ('Johnson', 'Peter',5, 123456789, 'UGRD', 'COMP-SCI', 'Chicago', 2004); 
insert into student 
    values ('Winter', 'Abigail', 11035, 111111111, 'GRD', 'PHD', 'Chicago', 2003); 
insert into student 
    values ('Patel', 'Prakash', 75234, null, 'UGRD', 'COMP-SCI', 'Chicago', 2001); 
insert into student 
    values ('Snowdon', 'Jennifer', 93321, 321321321, 'GRD', 'COMP-SCI', 'Springfield', 2004); 

insert into enrolled 
    values (11035, 1020, 'Fall', 2005); 
insert into enrolled 
    values (11035, 1092, 'Fall', 2005); 
insert into enrolled 
    values (11035, 8772, 'Spring', 2006); 
insert into enrolled 
    values (75234, 3201, 'Winter', 2006); 
insert into enrolled 
    values (08871, 1092, 'Fall', 2005); 
insert into enrolled 
    values (90421, 8772, 'Spring', 2006); 
insert into enrolled 
    values (90421, 2987, 'Spring', 2006); 

我的目標是：清單（對）已採取同班同學一起。

預期輸出：

StudentID COURSEID 
11035 1092 
8871 1092 
11035 8772 
90421 8772 

我怎樣才能做到這一點？

感謝，

Answer 1

請嘗試查詢：

select * from(
    select a.FirstName, a.LastName, b.StudentID, b.COURSEID, count(*) over (partition by b.COURSEID) CNum 
    from STUDENT a inner join enrolled b on a.SID=b.StudentID 
) x where CNum=2