SET SERVEROUTPUT  ON;
DECLARE
    v_salary NUMBER(0);
BEGIN
    SELECT salary INTO v_salary FROM employees -- We select from the table of employees the value of salary and put in variable v_salary
    WHERE employee_id = 100; -- we can not put all salaries in one variable, so we select the salary of the employee id equal with 100
    DBMS_OUTPUT.PUT_LINE(v_salary); -- we output the salary stored in the variable
EXCEPTION
END;