为什么它说“逗号在此位置无效”（位置如下所示）

Question

错误警告显示在第三行'title_id'

CREATE TABLE books(
book_id INT PRIMARY KEY,
title_id, #it gives the error warning here.
publisher_id,
author_id,
book_type VARCHAR (50), #aka ebook/hard/paper
genre_id,
FOREIGN KEY(genre_id) REFERENCES genres(genre_id),
FOREIGN KEY(author_id) REFERENCES author(author_id),
FOREIGN KEY(publisher_id) REFERENCES publishers(publisher_id),
FOREIGN KEY(title_id) REFERENCES title(title_id));

我还没有真正创建表格。我不太确定这是怎么回事

Answer 1

您遇到了错误，因为您没有指定“title_id”和其他一些列的数据类型。要解决此问题，请尝试以下操作：

CREATE TABLE books (
    book_id INT PRIMARY KEY,
    title_id INT,  -- Specify the data type (INT) here
    publisher_id INT,
    author_id INT,
    book_type VARCHAR(50),
    genre_id INT,
    FOREIGN KEY (genre_id) REFERENCES genres(genre_id),
    FOREIGN KEY (author_id) REFERENCES author(author_id),
    FOREIGN KEY (publisher_id) REFERENCES publishers(publisher_id),
    FOREIGN KEY (title_id) REFERENCES title(title_id)
);