删除 Oracle DB 中由外键添加的重复项

Question

我正在处理 Oracle DB 中的一个宿舍项目，我有 2 个表（学生、房间），当我运行查询以获取学生姓名、提供给他们的房间 ID 和设施时，它返回重复的学生姓名使用所有设施并且在查询中几乎没有编辑它会返回重复的设施。

如何修复这些重复项？ 这是代码

    --CREATE TABLE STUDENTS
    Create table students(
    regno integer primary key,
    name varchar2(30),
    phonenum number,
    address varchar2(30),
    roomalloc number 
    );

    Alter Table students Add CONSTRAINT fk_roomalloc
    FOREIGN KEY (roomalloc)
    REFERENCES rooms(roomno);

    Alter table students drop constraint fk_roomalloc

    --ALTER TABLE STUDENTS ADD JOIN DATE
    alter table students add (joindate Date);

    --Alter Table for Gender
    Alter Table students add(gender varchar2(2));
    Alter Table students MODIFY gender NOT NULL;

    --Constraint on Gender
    Alter Table students Add CONSTRAINT gen 
    Check (gender IN('M','F','m','f'));
    Alter Table students MODIFY mess default 'M';

    --Constraint Gender Check for Room Allocation
    Alter Table students Add CONSTRAINTS gen_check
    Check (Room IN(Gender='M' , 'Gender='F'));

    --Constraints:ADD MESS AS TRUE/FALSE
    ALTER TABLE students ADD (mess varchar2(4));
    Alter Table students Add CONSTRAINT mess_present 
    Check (mess IN('Yes','No','yes','no'));
    Alter Table students MODIFY mess default 'No';

    --Drop Constraint
    ALTER TABLE students
    DROP CONSTRAINT mess_present
    --ALTER TABLE NAME AS NOT NULL
    alter table students MODIFY name NOT NULL;
    --ALTER TABLE PHONE NO
    alter table students MODIFY phonenum UNIQUE;
    --ALTER TABLE Room Allocated
    alter table students MODIFY roomalloc Not Null;

    Describe students;

    --DATA ENTRY and Modification
    INSERT INTO students(regno, name, phonenum, address, roomalloc,joindate,mess)
        VALUES (1, 'Haseeb', 012345678,'Rawalpindi',1,'1-sep-14','No');
    INSERT INTO students(regno, name, phonenum, address, roomalloc,joindate)
        VALUES (2, 'Faisal', 03451111111,'Rawalpindi',1,'12-sep-14');
    INSERT INTO students(regno, name, phonenum, address, roomalloc,joindate)
        VALUES (3, 'Shahbaz', 03313214567,'Khewra',1,'15-feb-15');
    INSERT INTO students(regno, name, phonenum, address, roomalloc,joindate)
        VALUES (4, 'Muhaddas', 01235131237,'Kashmir',1,'15-feb-15');
    INSERT INTO students(regno, name, phonenum, address, roomalloc,joindate,mess)
        VALUES (5, 'Haseem', 01254530987,'Islamabad',2,'15-sep-15','Yes');
    INSERT INTO students(regno, name, phonenum, address, roomalloc,joindate,mess)
        VALUES (6, 'Asim', 03341234567,'Muzzafargarh',3,'15-sep-14','Yes');
    INSERT INTO students(regno, name, phonenum, address, roomalloc,joindate,mess)
        VALUES (7, 'Izza', 01231234564,'Sialkot',25,'15-sep-15','Yes');
    INSERT INTO students(regno, name, phonenum, address, roomalloc,joindate,mess)
        VALUES (8, 'Sara', 01231234561,'Narrowal',25,'15-sep-15','Yes');
    INSERT INTO students(regno, name, phonenum, address, roomalloc,joindate,mess)
        VALUES (9, 'Maria', 01231234567,'Wah',4,'25-sep-15','Yes');
    INSERT INTO students(regno, name, phonenum, address,    roomalloc,joindate,Gender)
        VALUES (10, 'Faha', 0123123452,'Okara',4,'26-sep-15','F');

    Update students SET Gender='M' WHERE regno>=1 And regno<=6;
    Update students SET roomalloc=4,Gender='F' WHERE regno>=7 And regno<=9;

    Describe students;

    --Data Fetching Queries

    Select *
    From students,rooms
    Where rooms.facility='Fan/Net/TV'
    ORDER BY roomalloc , regno;

    Drop table students;

    --CREATE TABLE Rooms
    Create table rooms(
    roomno integer primary key,
    facility varchar2(30)
    );

    --Altering Rooms Types
    Alter Table rooms Add CONSTRAINT rtype 
    Check (facility IN('AC/Net/TV','Fan/Net/TV','Fan/Net'));
    Alter Table rooms MODIFY facility default 'Fan/Net';

    Alter table rooms drop constraint str

    INSERT INTO rooms( roomno, facility)
        VALUES (1,'AC/Net/TV');

    INSERT INTO rooms( roomno, facility)
        VALUES (2,'Fan/Net/TV');

    INSERT INTO rooms( roomno, facility)
        VALUES (3,'Fan/Net/TV');

    INSERT INTO rooms( roomno, facility)
        VALUES (4,'Fan/Net');

    Alter table rooms Modify facility UNIQUE 

    Select *
    From rooms;

    Select students.name,rooms.facility
    From students,rooms
    Where roomno=4;

    Drop table rooms

Answer 1

您需要正确连接表格以获得所需的结果：

Select students.name,rooms.facility
From students join rooms on students.roomalloc = rooms.roomno
Where rooms.roomno=4;