Tables whose sole purpose is specify a subset of another table

Question

The database I\'m designing has an employees table; there can be multiple types of employees, one of which are medical employees. The database needs to also des

Answer 1

Why a separate table for that. Why not just create a BIT/Boolean field say IsMedical and set that to TRUE for medical employees in employee table like

/* Defines a generic employee */
CREATE TABLE employees (
    id      INT PRIMARY KEY AUTO_INCREMENT,
    name    VARCHAR(100) NOT NULL,
    IsMedical BIT(1)
);

That way, say if you want to get all medical employees from Employee table; you will just have to do a single filter in WHERE condition saying WHERE IsMedical = true. Whereas, if you go by a separate table then you will have perform a INNER JOIN with medical_employees and employees table which I believe would be more costly and unnecessary.