减号,联盟和交叉点

Question

我目前正在做以下作业:

CREATE TABLE T_1
(COURSE_NO CHAR(8) PRIMARY KEY,
COURSE_NAME CHAR(50) );

CREATE TABLE T_2
(COURSE_NO CHAR(8),
COURSE_NAME CHAR(50) );

CREATE TABLE T_3
(COURSE_NO CHAR(8),
STUDENT_ID CHAR(15),
GRADE CHAR (2));

INSERT INTO T_1
VALUES
('CS100','Data Structures'),
('CS200','Object Oriented Programming'),
('CS300','Distributed Systems'),
('EE100','Circuit Analysis'),
('EE200','VLSI Design'),
('EE300','Packet Switching Networks');

INSERT INTO T_2
VALUES
('EE100','Circuit Analysis'),
('EE200','VLSI Design'),
('EE300','Packet Switching Networks'),
('MA100','Calculus'),
('MA200','Advanced Calculus'),
('MA300','Number Theory');

INSERT INTO T_3
VALUES
('CS100','150-70-5879','B'),
('CS100','280-90-8766','A'),
('EE100','430-76-6858','B'),
('CS200','720-60-5000','B');

我被要求指定给定的元组:(T1-T2)联合(T2-T1)联合(T1与T2相交).

现在我知道MySQL使用了,或者为减号运算符加入,我能够以自己的方式处理每个减号,如:

SELECT *
FROM T_1
LEFT JOIN T_2
ON T_1.Course_No = T_2.Course_no
WHERE T_2.Course_no IS NULL;

我也可以为T2-T1做这个,但是当我在1个查询中完成所有操作或者如何(T1-T2)U(T2-T1)或(T2-T1)U(T1nT2)时我都迷失了.

有帮助吗？

Answer 1

Ť ₁ ∖Ť ₂

Ť ₂ ∖Ť ₁

Ť ₁ ∩Ť ₂

因此(T ₁ ∖Ť ₂)∪(T ₂ ∖Ť ₁)∪(T ₁ ∩Ť ₂)= T ₁ ∪Ť ₂:

SELECT * FROM T_1 UNION SELECT * FROM T_2

在sqlfiddle上看到它.