Table sizes in oracle

To find out how much physical space a table occupies in Oracle Database, use the following query :

SELECT
owner, table_name, segment_type,TRUNC(sum(bytes)/1024/1024) MEG
FROM
(SELECT segment_name table_name, owner, bytes, segment_type
FROM dba_segments
)
WHERE owner in UPPER(SCHEMA_NAME)
GROUP BY table_name,segment_type, owner
HAVING SUM(bytes)/1024/1024 >= 10
ORDER BY SUM(bytes) desc;


This will return all the tables in the schema that occupy more than 10 MB of space.