postgresql多个子查询

Question

我手头有一项任务,要求我返回一名学生的详细信息,该学生就读于由霍夫曼姓氏老师教授的课程中,我被困住了.

    SELECT * FROM Public."Class" WHERE tid=(
        SELECT tid FROM Public."Tutor" WHERE tname LIKE '%Hoffman');

这让我回到霍夫曼教授的课程,但从这里我不知道该往哪里去.我相信我必须访问'注册'表,然后最终访问学生表,但试图无济于事.以下查询是在我打破查询之前得到的-_-我确定我将不得不使用HAVINGor IN关键字,但我不知道如何处理它们!

SELECT * FROM Public."Student" WHERE programme='IT' (
    SELECT * FROM Public."Class" WHERE tid=(
        SELECT tid FROM Public."Tutor" WHERE tname LIKE '%Hoffman')
    );

任何帮助将非常感激!

数据库结构如下: -

Student(sid integer, sname varchar(20), programme varchar(4), level integer, age integer) 
Class(ccode varchar(6), cname varchar(25), week_day varchar(3), meets_at time, room 
varchar(6), tid integer) 
Enrolled(sid integer, ccode varchar(6)) 
Tutor(tid integer, tname varchar(20))

再次感谢 :)

更新: -

SELECT DISTINCT *
FROM Public."Student" s
INNER JOIN Public."Enrolled" e ON e.sid = s.sid
INNER JOIN Public."Class" c ON c.ccode = e.ccode
INNER JOIN Public."Tutor" t ON t.tid = c.tid
WHERE programme='IT' AND t.tname LIKE '%Hoffman';

Answer 1

您不需要为每个验证执行子查询.这可以通过JOINS轻松完成:

SELECT s.*
FROM Student s
INNER JOIN Enrolled e ON e.sid = s.sid
INNER JOIN Class c ON c.ccode = e.ccode
INNER JOIN Tutor t ON t.tid = c.tid
WHERE t.tname LIKE '%Hoffman';