viewAllEmployees() {
		return this.connection.query(
			`
            SELECT
                e1.id AS ID,
                e1.first_name AS First_Name,
                e1.last_name AS Last_Name,
                role.title AS Role,
                department.name AS Department,
                CONCAT(e2.first_name, ' ', e2.last_name) AS Manager,
                role.salary AS Salary
            FROM
                employee e1
            LEFT JOIN
                role ON e1.role_id = role.id
            LEFT JOIN
                employee e2 ON e1.manager_id = e2.id
		    LEFT JOIN department ON role.department_id = department.id
		    ORDER BY
                e1.id;
        `
		);
    }
// View all employees and all employees details by joining employee, role and department tables.
View all employees and all employees details by joining employee, role and department tables.
View all employees and all employees details by joining employee role and department tables .
viewAllEmployees() {
		return this.connection.query(
			`
            SELECT
                e1.id AS ID,
                e1.first_name AS First_Name,
                e1.last_name AS Last_Name,
                role.title AS Role,
                department.name AS Department,
                CONCAT(e2.first_name, ' ', e2.last_name) AS Manager,
                role.salary AS Salary
            FROM
                employee e1
            LEFT JOIN
                role ON e1.role_id = role.id
            LEFT JOIN
                employee e2 ON e1.manager_id = e2.id
		    LEFT JOIN department ON role.department_id = department.id
		    ORDER BY
                e1.id;
        `
		);
    }
viewAllEmployees ( ) { return this . connection . query ( ` ` ) ; }
View all employees and all employees details by joining employee, role and department tables.
View all employees and all employees details by joining employee role and department tables .