Question

我真的很难为大学建立我的第一个数据库。我将必须参考公司和员工的钥匙才能工作。在一种关系中，员工只能在一家公司工作。

我经常遇到一些错误，一个是在主键之后出现的，而且引用并没有真正起作用。

仅供参考：我正在研究PostgreSQL。

我希望有人能帮助我。感谢您的帮助

CREATE SCHEMA p10_1_employee;
Set search_path to p10_1_employee;

CREATE TABLE employee(
    firstname varchar(20) NOT NULL,
    lastname varchar(20) NOT NULL,
    CONSTRAINT cPKfirstnamelastname PRIMARY KEY(firstname, lastname)
);

CREATE TABLE company(
    companyname varchar(20) NOT NULL,
    CONSTRAINT cPKcompanyname PRIMARY KEY (companyname)
);

CREATE TABLE works (
    personenname varchar(40),
    companyname varchar(20)
    CONSTRAINT cPKpersonennamecompanyname PRIMARY KEY (personenname, companyname)
    CONSTRAINT cFKfirstnamelastname FOREIGN KEY (personenname) REFERENCES employee(firstname, lastname),
    CONSTRAINT cFKcompanyname FOREIGN KEY (companyname) REFERENCES company(companyname)
);

Answer 1

works表中存在多个错误（缺少逗号和错误的引用列数）。这是一个有效的脚本

CREATE TABLE works (
    personenname_firstname varchar(20),
    personenname_lastname varchar(40),
    companyname varchar(20),
    CONSTRAINT cPKpersonennamecompanyname PRIMARY KEY (personenname_firstname, personenname_lastname, companyname),
    CONSTRAINT cFKfirstnamelastname FOREIGN KEY (personenname_firstname, personenname_lastname) REFERENCES employee,
    CONSTRAINT cFKcompanyname FOREIGN KEY (companyname) REFERENCES company
);

参考，主键和外键

1 个答案: