Oracle Query LOB Field size

SELECT DISTINCT AB. TABLE_NAME,
Ab. Segment_name,
Ab. Tablespace_name,
Ab. OWNER,
Sum (AC. bytes/1024/1024/1024) GB
From Dba_lobs AB, dba_segments AC
where AB. OWNER in (SELECT USERNAME
From Dba_users A
WHERE a.account_status = ' OPEN '
and A.default_tablespace not in
(' SYSTEM ',
' USERS ',
' Sysaux ',))
and AB. Segment_name = Ac.segment_name
and AB. OWNER = Ac.owner
--and AB. Tablespace_name = ' Lob_data '
GROUP by AB. TABLE_NAME, AB. Segment_name, AB. Tablespace_name, AB. OWNER
ORDER BY 5 Desc

---Querying single-partition LOB field sizes for single-table (partitioned tables)

SELECT DLP. TABLE_NAME,
Dlp. COLUMN_NAME,
Dlp. Partition_name,
Ds. bytes/1024/1024/1024 GB
From Dba_lob_partitions DLP
Left JOIN dba_segments DS
On (DLP. Lob_partition_name = DS. Partition_name)
WHERE DLP. table_name = ' T_test
and DS. segment_name = ' sys_lob0000318949c00003$$ ';

Oracle Query LOB Field size