SQL การใช้งาน NOT Operator

CREATE TABLE Employees (
    EmployeeID INT PRIMARY KEY,
    Name VARCHAR(100),
    Age INT,
    Department VARCHAR(50),
    Salary DECIMAL(10, 2)
);

INSERT INTO Employees (EmployeeID, Name, Age, Department, Salary) VALUES
(1, 'John Doe', 28, 'HR', 45000),
(2, 'Jane Smith', 35, 'IT', 55000),
(3, 'Alice Brown', 25, 'Finance', 32000),
(4, 'Bob White', 40, 'IT', 60000),
(5, 'Charlie Green', 29, 'HR', 40000);

SELECT * FROM Employees
WHERE NOT Age >= 30;

SELECT * FROM Employees
WHERE Department NOT IN ('HR', 'Finance');

SELECT * FROM Employees
WHERE Name NOT LIKE 'J%';

SELECT * FROM Employees
WHERE Salary NOT BETWEEN 30000 AND 50000;

-- สร้างตาราง Managers
CREATE TABLE Managers (
    ManagerID INT PRIMARY KEY,
    EmployeeID INT
);

-- แทรกข้อมูลลงในตาราง Managers
INSERT INTO Managers (ManagerID, EmployeeID) 
VALUES 
(1, 2),
(2, 4);

SELECT * FROM Employees e
WHERE NOT EXISTS (
  SELECT 1 FROM Managers m WHERE m.EmployeeID = e.EmployeeID
);