SELECT table_name as Table_Name, row_cnt as Row_Count, SUM(mb) as Size_MB
FROM
(SELECT in_tbl.table_name, to_number(extractvalue(xmltype(dbms_xmlgen.getxml('select count(*) c from ' ||ut.table_name)),'/ROWSET/ROW/C')) AS row_cnt , mb
FROM
(SELECT CASE WHEN lob_tables IS NULL THEN table_name WHEN lob_tables IS NOT NULL THEN lob_tables END AS table_name , mb
FROM (SELECT ul.table_name AS lob_tables, us.segment_name AS table_name , us.bytes/1024/1024 MB FROM user_segments us
LEFT JOIN user_lobs ul ON us.segment_name = ul.segment_name ) ) in_tbl INNER JOIN user_tables ut ON in_tbl.table_name = ut.table_name ) GROUP BY table_name, row_cnt ORDER BY 3 DESC;``
Above query will give, Table_name, Row_count, Size_in_MB(includes lob column size) of specific user.