Calculate table sizes

SELECT owner,
       table_name,
       TRUNC(sum(bytes)/1024/1024)  Meg
FROM (
 SELECT segment_name table_name,
        owner,
        bytes
 FROM   dba_segments
 WHERE  segment_type = 'TABLE'
 UNION ALL
 SELECT i.table_name,
        i.owner,
        s.bytes
 FROM   dba_indexes   i,
        dba_segments  s
 WHERE  s.segment_name = i.index_name
 AND    s.owner        = i.owner
 AND    s.segment_type = 'INDEX'
 UNION ALL
 SELECT l.table_name,
        l.owner,
        s.bytes
 FROM   dba_lobs l, dba_segments s
 WHERE  s.segment_name = l.segment_name
 AND    s.owner        = l.owner
 AND    s.segment_type = 'LOBSEGMENT'
 UNION ALL
 SELECT l.table_name,
        l.owner,
        s.bytes
 FROM   dba_lobs       l,
        dba_segments   s
 WHERE  s.segment_name = l.index_name
 AND    s.owner        = l.owner
 AND    s.segment_type = 'LOBINDEX')
WHERE owner in UPPER(:owner)
GROUP BY table_name, owner
HAVING SUM(bytes)/1024/1024 > 10  -- Ignore small tables
ORDER BY SUM(bytes) desc;