根据多个属性定义 SQL 约束

Question

我有这个定义的类型和表：

CREATE TYPE emp_role AS ENUM ('Manager','Developer','Accountant','Secretary');
CREATE TABLE employees (
employee_id int NOT NULL UNIQUE,
lastname text NOT NULL,
firstname text NOT NULL,
address text NOT NULL,
hire_date date NOT NULL,
salary numeric NOT NULL CHECK(salary > 1.500), 
emp_role emp_role,
department_id int NOT NULL
);

我想在这个表上创建一个约束，而不修改它的定义，它同时依赖于属性hire_date、salary和emp_role，这意味着例如具有emp_role的员工Manager 在2019-21-11 之后聘用的salary不能比15.000大，所以这样的查询应该返回错误：

INSERT INTO employees VALUES(2,'foo','bar','foostreet','2019-12-20',18.0000,'Manager',3);

我不知道怎么做

Answer 1

您可以按如下方式创建多列检查约束：

CREATE TYPE emp_role AS ENUM ('Manager','Developer','Accountant','Secretary');

CREATE TABLE employees (
    employee_id int NOT NULL UNIQUE,
    lastname text NOT NULL,
    firstname text NOT NULL,
    address text NOT NULL,
    hire_date date NOT NULL,
    salary numeric NOT NULL CHECK(salary > 1500), 
    emp_role emp_role,
    department_id int NOT NULL
    CONSTRAINT CK_employee CHECK (
        NOT(
            emp_role = 'Manager' 
            AND hire_date > DATE'2019-11-21' 
            AND salary > 15000
        )
    )
);

Demo on DB Fiddle

INSERT INTO employees VALUES(2,'foo','bar','foostreet','2019-12-20',180000,'Manager',3);

错误：关系“员工”的新行违反检​​查约束“ck_employee” 详细信息：失败行包含 (2, foo, bar, foostreet, 2019-12-20, 180000, Manager, 3)。

INSERT INTO employees VALUES(2,'foo','bar','foostreet','2019-12-20',1,'Developer',3);

错误：关系“employees”的新行违反了检查约束“employees_salary_check” 详细信息：失败行包含 (2, foo, bar, foostreet, 2019-12-20, 1, Developer, 3)。