[sql] Oracle DateTime in Where Clause?

I have sql something like this:

SELECT EMP_NAME, DEPT
FROM EMPLOYEE
WHERE TIME_CREATED >= TO_DATE('26/JAN/2011','dd/mon/yyyy')

-> This returns 10 rows and TIME_CREATED = '26-JAN-2011'

Now when i do this i don't get any rows back,

SELECT EMP_NAME, DEPT
    FROM EMPLOYEE
    WHERE TIME_CREATED = TO_DATE('26/JAN/2011','dd/mon/yyyy')

-> Took the greater than out

Any reason why?

As other people have commented above, using TRUNC will prevent the use of indexes (if there was an index on TIME_CREATED). To avoid that problem, the query can be structured as

SELECT EMP_NAME, DEPT
FROM EMPLOYEE
WHERE TIME_CREATED BETWEEN TO_DATE('26/JAN/2011','dd/mon/yyyy') 
            AND TO_DATE('26/JAN/2011','dd/mon/yyyy') + INTERVAL '86399' second;

86399 being 1 second less than the number of seconds in a day.

You could also do:

SELECT EMP_NAME, DEPT
FROM EMPLOYEE
WHERE TRUNC(TIME_CREATED) = DATE '2011-01-26'

This is because a DATE column in Oracle also contains a time part. The result of the to_date() function is a date with the time set to 00:00:00 and thus it probably doesn't match any rows in the table.

You should use:

SELECT EMP_NAME, DEPT
FROM EMPLOYEE
WHERE trunc(TIME_CREATED) = TO_DATE('26/JAN/2011','dd/mon/yyyy')

You can also use the following to include the TIME portion in your query:

SELECT EMP_NAME
     , DEPT
  FROM EMPLOYEE 
 WHERE TIME_CREATED >= TO_DATE('26/JAN/2011 00:00:00', 'dd/mon/yyyy HH24:MI:SS');