Selecting rows of a particular day

Question

I have always had problems when dealing with dates :p (Ok pun intended)
I have table which has a date field in the format:
DD/MM/YYYY hh:mm:ss
How can I select only the rows which have the date 20/08/2004 ?

Answer 1

Hello
The internal format of a date column does not change, every single date is recorded with the century, year, month,day, hour, minute, second. The only thing that changes is the way you display it. Anyway, if you want to get rows with a specific date, regardless of the time you can do a few things.
SELECT
     column
FROM
     table
WHERE
     TRUNC(date_col) = TO_DATE('28/08/2004','DD/MM/YYYY');This works by truncating the time portion of the date value to be midnight. If you "create" a date value without specifying the time, it will default to midnight too. The only problem with using TRUNC on date_col is that oracle will not be able to use any indexes on that column (unless there is a function index on it using TRUNC)
To make sure that oracle is able to use any indexes on the date column you need to set up a range from midnight to 23:59:59 on the day you are searching, either of the following will do that...
SELECT
     column
FROM
     table
WHERE
     date_col BETWEEN TO_DATE('28/08/2004','DD/MM/YYYY') AND TO_DATE('28/08/2004 23:59:59','DD/MM/YYYY HH24:MI:SS');
SELECT
     column
FROM
     table
WHERE
     date_col >= TO_DATE('28/08/2004','DD/MM/YYYY')
AND 
     date_col < TO_DATE('29/08/2004','DD/MM/YYYY');For the last example, if you are using a variable to store the search date, you can do the following which just means less typing...
SELECT
     column
FROM
     table
WHERE
     date_col >= SearchDateVar
AND 
     date_col < SearchDateVar + 1;HTH