SELECT
distinct table_name,
TO_NUMBER(
extractvalue(
xmltype(
dbms_xmlgen.getxml('SELECT COUNT(*) c FROM '||table_name))
,'/ROWSET/ROW/C')) rec_ccount,
trunc(bytes/1024,0) tablesize
FROM user_tables
join user_segments on user_segments.segment_name = user_tables.table_name
order by rec_ccount desc;