How to find table size on oracle database (12.2 & 18c)?

Question : How to find table size on oracle database (12.2,18c)?

Answer : By using below query you will table size on oracle database

Query: select segment_name,segment_type,bytes/1024/1024/1024 GB from dba_segments where segment_type='TABLE' and segment_name='TEST_TAB';

Output:

SQL>select segment_name,segment_type,bytes/1024/1024/1024 GB from dba_segments where segment_type='TABLE' and segment_name='TEST_TAB';

SEGMENT_NAME         SEGMENT_TYPE               GB
-------------------- ------------------ ----------
TEST_TAB_DATA        TABLE              108.838806