Oracle Database Discussions

Hello,
I am using ORACLE 11g Standard edition and RHEL 4.

I have a situation in which i want to know the size of the limited rows of the table.

I am moving table's rows from one table(one tablespace) to another table(another tablespace) While moving the rows I want to be sure that the size of the rows is good enough to fit in the another table's tablespace free size. So before inserting rows in another table i will check the size of rows and the free space in tablespace and perform the action as per.

Here is the senario with example :-

I have a table called MAIN_TAB which has a column as DATE_TIME which stores the systimestamp when the data was inserted. See the code below ...

select * from main_tab;

ID     VALUE DATE_TIME
----    ---------  ----------------------------------------------------
1	DATA	 18-MAY-11 12.00.00.000000000 AM
2	DATA	 18-MAY-11 12.00.00.000000000 AM
3	DATA	 17-MAY-11 12.00.00.000000000 AM
4	DATA	 17-MAY-11 12.00.00.000000000 AM

Now i will fire a group by date_time query to know how many rows for each systimestamp.

select trunc(date_time),count(id)
from MAIN_TAB
group by trunc(date_time)
DATE_TIME     COUNT(ID)
------------------    ----------------
17-MAY-11	          2
18-MAY-11	          2

So now you can see i have 2 rows for 17th and 18th May. I want to know what is the size of the data for 17th and 18th May in MB. I know how to get the size of the whole table but i want only the limited rows size as per date.

So the question is how can i get the size of a table's 2 rows data ???

Provide me some guidance.

If the question is not clear to you , let me know ....

Thanks in advance ...