Query the table size and tablespace size in Oracle. | medium | small

The table size has two meanings. One is the number of physical spaces allocated to a table, regardless of whether the space is used or not. You can query the number of bytes as follows:
Select segment_name, bytes
From user_segments
Where segment_type = 'table ';
Or
Select segment_name, sum (bytes)/1024/1024 from user_extents group by segment_name
Space actually used by another table. Query as follows:
Analyze table EMP compute statistics;
Select num_rows * avg_row_len
From user_tables
Where table_name = 'emp ';
View the size of each tablespace
Select tablespace_name, sum (bytes)/1024/1024 from dba_segments group by tablespace_name