Função Oracle TRUNC

SELECT first_name,
       salary / 2.7,
 ROUND(salary / 2.7) AS ROUND,
 TRUNC(salary / 2.7) AS TRUNC
  FROM hr.employees
 WHERE job_id ='IT_PROG';

SELECT first_name,
       salary / 2.7,
 ROUND(salary / 2.7, 2) AS ROUND,
 TRUNC(salary / 2.7, 2) AS TRUNC
  FROM hr.employees
 WHERE job_id ='IT_PROG';

SELECT first_name,
       hire_date,
 ROUND(hire_date, 'MONTH') AS ROUND,
 TRUNC(hire_date, 'MONTH') AS TRUNC
  FROM hr.employees
 WHERE job_id ='IT_PROG';

SELECT first_name,
       hire_date,
 ROUND(hire_date, 'DAY') AS ROUND,
 TRUNC(hire_date, 'DAY') AS TRUNC
  FROM hr.employees
 WHERE job_id ='IT_PROG';

SELECT first_name,
       hire_date,
 ROUND(hire_date, 'YYYY') AS ROUND,
 TRUNC(hire_date, 'YYYY') AS TRUNC
  FROM hr.employees
 WHERE job_id ='IT_PROG';