Getting the Size of a Database

I recently needed to get an estimated size of an Oracle database. It turns out to be not too hard.

--by table
select table_name, num_rows, avg_row_len,
 ROUND((num_rows * avg_row_len / 1048576),2) "MB Used"
from user_tables
where num_rows > 0

--total
select SUM(ROUND((num_rows * avg_row_len / 1048576),2)) "Total MB Used"
from user_tables