SQL GROUP BY QUERY 未返回所需的输出

Question

这是我的表格和插入值:

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', 32105, 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);

我有以下查询:

SELECT e.studentid
FROM enrolled e 
FULL OUTER JOIN student s ON e.studentid = s.sid 
WHERE ((e.quarter = 'Fall') OR (e.quarter = 'Spring')) 
GROUP BY e.studentid 
HAVING count(e.studentid) = 1;

但这只会返回

8871

这应该返回

8871
90421

此查询的目标是:列出在秋季学期至少注册了一门类(class)或在 Spring 学期注册至少一门类(class)的学生，但不能同时注册这两个类(class)。您将不得不添加几行来测试您的查询。

如有任何帮助，我们将不胜感激。谢谢。

Answer 1

试一试

SELECT  a.SID
FROM    student a
        INNER JOIN enrolled b
            ON a.SID = b.StudentID
WHERE   b.quarter IN ('Fall', 'Spring')
GROUP   BY a.SID
HAVING  COUNT(DISTINCT b.quarter) = 1