Question

我有以下表格：

付款表

CREATE TABLE Payment (
    PayID INTEGER,
PayName CHAR (55),
PaymentDescription VARCHAR (100),
    Primary Key (PayID)
);

用户表

CREATE TABLE Users (
    UserID INTEGER, 
    UserFirst CHAR (40),
    UserLast CHAR (40),
    UserName VARCHAR (40),
    UserAddress VARCHAR (35),
    UserBirthdate DATE,
    UserGender CHAR (1),
    UserEmail VARCHAR (35),
    PRIMARY KEY (UserID)
);

流派表

CREATE TABLE GENRE (
    GenreID Integer,
    Name CHAR(45),
    Description VARCHAR (250),
    PRIMARY KEY (GenreID)
);

歌曲表

CREATE TABLE SONG (
    SongID Integer,
    GenreID Integer,
    Title VARCHAR (50),
    Album VARCHAR (40),
    Duration TIME,
    ReleaseYear DATE,
    PRIMARY KEY (SongID),
    CONSTRAINT foreignkey_holds_GenreID FOREIGN KEY (GenreID) 
    REFERENCES Genre(GenreID)
);

Song_Users表

CREATE TABLE Song_Users (
UserID INTEGER, 
SongID Integer,
PRIMARY KEY (UserID,SongID),
CONSTRAINT fk_users_song_user FOREIGN KEY (UserID) 
    REFERENCES Users(UserID),
CONSTRAINT fk_users_song_song FOREIGN KEY (SongID) 
    REFERENCES SONG(SongID)
);

Payment_Users表

CREATE TABLE Payment_Users (
UserID INTEGER,
PayID INTEGER,
PRIMARY KEY (UserID,PayID),
CONSTRAINT fk_users_payment_user FOREIGN KEY (UserID) 
    REFERENCES Users(UserID),
CONSTRAINT fk_users_payment_pay FOREIGN KEY (PayID) 
    REFERENCES Payment(PayID)
);

我还填写了表格：

付款

INSERT INTO Payment (PayID,PayName,PaymentDescription) VALUES (1, 'Visa', 'Applies to VISA Debit, Electron, Credit')

INSERT INTO Payment (PayID,PayName,PaymentDescription) VALUES (2, 'Mastercard', 'Applies across all types')


INSERT INTO Payment (PayID,PayName,PaymentDescription) VALUES (3, 'PayPal', 'Payment made using PayPal')

INSERT INTO Payment (PayID,PayName,PaymentDescription) VALUES (4, 'ApplePay', 'Payment method for IOS users')

用户

INSERT INTO Users (UserID, UserFirst, UserLast, UserName, UserAddress, UserBirthdate, UserGender, UserEmail) VALUES (1, 'Jane', 'Johnson', 'jjsweet135', '10 House Wood Street',19970321, 'F', 'jj1997@gmail.com')


INSERT INTO Users (UserID, UserFirst, UserLast, UserName, UserAddress, UserBirthdate, UserGender, UserEmail) VALUES (2, 'Joe', 'Watson', 'joewatson98', '21 House Red Street',19980414, 'M', 'joewatson1998@gmail.com')


INSERT INTO Users (UserID, UserFirst, UserLast, UserName, UserAddress, UserBirthdate, UserGender, UserEmail) VALUES (3, 'Katie', 'Davies', 'katiethebest425', '17 House Fun Street',20000318, 'F', 'katiebest452@hotmail.com')

INSERT INTO Users (UserID, UserFirst, UserLast, UserName, UserAddress, UserBirthdate, UserGender, UserEmail) VALUES (4, 'Tom', 'Branson', 'tommylad100', '27 House Church Street',20010719, 'M', 'tommylad35@orange.com')

流派表

INSERT INTO Genre (GenreID, Name, Description) VALUES  

(1, 'Electro Swing', 'A musical journey set in the 90s')

INSERT INTO Genre (GenreID, Name, Description) VALUES  

(2, 'House', 'When the beat shakes your house')

INSERT INTO Genre (GenreID, Name, Description) VALUES  

(3, 'Classical', 'To stimulate neural activity in your brain')


INSERT INTO Genre (GenreID, Name, Description) VALUES  

(4, 'Rap', 'Experience the streets from the comfort of your own home')


INSERT INTO Genre (GenreID, Name, Description) VALUES  

(5, 'Pop', 'Follow the status quo')

歌曲表

INSERT INTO SONG (SongID, GenreID, Title, Album, Duration, ReleaseYear) VALUES (1, 1, 'Swing the Electro', 'Electro Swing Vol 1', 11537, 19970316)


INSERT INTO SONG (SongID, GenreID, Title, Album, Duration, ReleaseYear) VALUES (2, 2, 'This is my House', 'UK House Anthem', 11454, 19990419)


INSERT INTO SONG (SongID, GenreID, Title, Album, Duration, ReleaseYear) VALUES (3, 3, 'Candy Shop', '50 Cent Classics', 2254, 20010324)

INSERT INTO SONG (SongID, GenreID, Title, Album, Duration, ReleaseYear) VALUES (4, 4, 'Mozart', 'Classical strokes', 44524, 18000225)

INSERT INTO SONG (SongID, GenreID, Title, Album, Duration, ReleaseYear) VALUES (5, 5, 'Katy Perry', 'Baby you are a Firework', 13524, 20050324)

INSERT INTO SONG (SongID, GenreID, Title, Album, Duration, ReleaseYear) VALUES (6, 5, 'One Direction', 'We are the one', 013204, 20060211)

INSERT INTO SONG (SongID, GenreID, Title, Album, Duration, ReleaseYear) VALUES (7, 5, 'Chainsmokers', 'In the back seat of your rover', 33544, 20160123)

INSERT INTO SONG (SongID, GenreID, Title, Album, Duration, ReleaseYear) VALUES (8, 5, 'Justin Bieber', 'Teenage dream', 22222, 20150325)

Song_Users表

INSERT INTO Song_Users (UserID, SongID) VALUES (1,1)

INSERT INTO Song_Users (UserID, SongID) VALUES (2,2)

INSERT INTO Song_Users (UserID, SongID) VALUES (3,3)

INSERT INTO Song_Users (UserID, SongID) VALUES (4,4)

INSERT INTO Song_Users (UserID, SongID) VALUES (4,1)

INSERT INTO Song_Users (UserID, SongID) VALUES (4,2)

INSERT INTO Song_Users (UserID, SongID) VALUES (4,3)


INSERT INTO Song_Users (UserID, SongID) VALUES (4,5)

INSERT INTO Song_Users (UserID, SongID) VALUES (4,6)

INSERT INTO Song_Users (UserID, SongID) VALUES (4,7)

INSERT INTO Song_Users (UserID, SongID) VALUES (4,8)

Payment_Users表

INSERT INTO Payment_Users VALUES (1,1)
INSERT INTO Payment_Users VALUES (2,2)
INSERT INTO Payment_Users VALUES (3,3)
INSERT INTO Payment_Users VALUES (4,3)

我需要为女性（F）找到最流行的音乐类型。我似乎无法检索此信息，因为没有相应的Genre外键（GenreID）。

我如何创建查询以获得女性中最受欢迎的类型？

修改

SELECT Users.UserID, UserGender, SongID, GenreID FROM Users, Song_Users, Song

WHERE Users.UserID = Song_Users.UserID 

AND 

WHERE Genre.GenreID = Song.GenreID;

我正在尝试将GenreID与SongID相关联，但我不知道该怎么做。有一个带外键的链接，但不在Genre表中，但仅在Song Table中。我的逻辑是选择用户，他们的性别，他们的歌曲，然后选择相应的流派。然后我可以使用像HAVING CLAUSE这样的东西选择严格的女性并使用COUNT（流派）和相应的GROUPBY函数

Answer 1

SELECT COUNT(g.`GenreID`) AS popularity, g.`Name`  FROM genre g, song_users su, song s, users u WHERE
u.`UserGender` = 'F' 
AND su.`UserID` = u.`UserID`
AND s.`SongID` = su.`SongID`
AND g.`GenreID` = s.`GenreID`
GROUP BY g.`GenreID`

受欢迎程度会给你流派的名称和他们的人数，最高的数量是最着名的。

Answer 2

根据上述评论，此问题中存在大量不必要的信息。应该包括一组示例数据和您努力的证据，但用于填充表的命令是无关紧要的。

我假设以下人气定义：以特定类型购买歌曲的用户数量最多。

根据上面的内容，您可以通过四个表格中的内部联接来完成您正在寻找的内容：

SELECT 
    count(u.UserID) as 'popularity', 
    g.Name as 'genre' 
FROM
    Users u INNER JOIN
    Song_Users su INNER JOIN
    SONG s INNER JOIN
    GENRE g
ON
    u.UserID = su.UserID,
    su.SongID = s.SongID,
    s.GenreID = g.GenreID
WHERE
    u.UserGender = 'F'
GROUP BY
    g.Name
ORDER BY
    count(u.UserID) DESC

Answer 3

你将在MYSQL内部加入，

从Songs Innerjoin users.user_id ON songs.user_id中选择字段名称 Innerjoin Genre.Genre_id ON songs.Genre_id 您会看到正确键入表名和列名称。您将获得正确的结果。

如何根据此标准检索数据？

3 个答案: