The difference of to_char

Question

Hi.
I do two selects on table emp. The first select is:
select ename
from emp
where hiredate<sysdate;
The second select is:
select ename
from emp
where to_char(hiredate,'DD.MM.YYYY')<to_char(hiredate,'DD.MM.YYYY');
The first select is right and it show me all employees.
But the second select show me only four employees. And I don't understand the result of the second select.

Answer 1

You can use TRUNC and ROUND functions.
SQL> alter session set NLS_DATE_FORMAT = 'dd-mm-yyyy:hh24:mi:ss';
Session altered.
SQL> select sysdate,
2 trunc(sysdate, 'DAY') trunc_date,
3 round(sysdate, 'day') round_date
4 from dual;
SYSDATE TRUNC_DATE ROUND_DATE
04-02-2004:17:08:29 02-02-2004:00:00:00 02-02-2004:00:00:00