SQL> create table t1 as select * from dba_tables;

Table created.

SQL> desc t1;

 Name                                                                   Null?    Type

 ----------------------------------------------------------------- -------- --------------------------------------------

 OWNER                                                                   NOT NULL VARCHAR2(30)

 TABLE_NAME                                                           NOT NULL VARCHAR2(30)

 TABLESPACE_NAME                                                            VARCHAR2(30)

 CLUSTER_NAME                                                                    VARCHAR2(30)

 IOT_NAME                                                                    VARCHAR2(30)

 STATUS                                                                     VARCHAR2(8)

 PCT_FREE                                                                    NUMBER

 PCT_USED                                                                    NUMBER

 INI_TRANS                                                                    NUMBER

 MAX_TRANS                                                                    NUMBER

 INITIAL_EXTENT                                                             NUMBER

 NEXT_EXTENT                                                                    NUMBER

 MIN_EXTENTS                                                                    NUMBER

 MAX_EXTENTS                                                                    NUMBER

 PCT_INCREASE                                                                    NUMBER

 FREELISTS                                                                    NUMBER

 FREELIST_GROUPS                                                            NUMBER

 LOGGING                                                                    VARCHAR2(3)

 BACKED_UP                                                                    VARCHAR2(1)

 NUM_ROWS                                                                    NUMBER

 BLOCKS                                                                     NUMBER

 EMPTY_BLOCKS                                                                    NUMBER

 AVG_SPACE                                                                    NUMBER

 CHAIN_CNT                                                                    NUMBER

 AVG_ROW_LEN                                                                    NUMBER

 AVG_SPACE_FREELIST_BLOCKS                                                    NUMBER

 NUM_FREELIST_BLOCKS                                                            NUMBER

 DEGREE                                                                     VARCHAR2(20)

 INSTANCES                                                                    VARCHAR2(20)

 CACHE                                                                            VARCHAR2(10)

 TABLE_LOCK                                                                    VARCHAR2(8)

 SAMPLE_SIZE                                                                    NUMBER

 LAST_ANALYZED                                                                    DATE

 PARTITIONED                                                                    VARCHAR2(3)

 IOT_TYPE                                                                    VARCHAR2(12)

 TEMPORARY                                                                    VARCHAR2(1)

 SECONDARY                                                                    VARCHAR2(1)

 NESTED                                                                     VARCHAR2(3)

 BUFFER_POOL                                                                    VARCHAR2(7)

 FLASH_CACHE                                                                    VARCHAR2(7)

 CELL_FLASH_CACHE                                                            VARCHAR2(7)

 ROW_MOVEMENT                                                                    VARCHAR2(8)

 GLOBAL_STATS                                                                    VARCHAR2(3)

 USER_STATS                                                                    VARCHAR2(3)

 DURATION                                                                    VARCHAR2(15)

 SKIP_CORRUPT                                                                    VARCHAR2(8)

 MONITORING                                                                    VARCHAR2(3)

 CLUSTER_OWNER                                                                    VARCHAR2(30)

 DEPENDENCIES                                                                    VARCHAR2(8)

 COMPRESSION                                                                    VARCHAR2(8)

 COMPRESS_FOR                                                                    VARCHAR2(12)

 DROPPED                                                                    VARCHAR2(3)

 READ_ONLY                                                                    VARCHAR2(3)

 SEGMENT_CREATED                                                            VARCHAR2(3)

 RESULT_CACHE                                                                    VARCHAR2(7)

SQL> comment on table t1 is 'it contents all tables for dba';

Comment created.

SQL> desc user_tab_comments;

 Name                                                                   Null?    Type

 ----------------------------------------------------------------- -------- --------------------------------------------

 TABLE_NAME                                                           NOT NULL VARCHAR2(30)

 TABLE_TYPE                                                                    VARCHAR2(11)

 COMMENTS                                                                    VARCHAR2(4000)

SQL> select * from user_tab_comments where table_name='T1';

TABLE_NAME                       TABLE_TYPE  COMMENTS

------------------------------ ----------- --------------------

T1                               TABLE           it contents all tabl

   es for dba

SQL> comment on column t1.table_name is 'this is the name fo the table';

Comment created.

SQL> desc user_col_comments;

 Name                                                                   Null?    Type

 ----------------------------------------------------------------- -------- --------------------------------------------

 TABLE_NAME                                                           NOT NULL VARCHAR2(30)

 COLUMN_NAME                                                           NOT NULL VARCHAR2(30)

 COMMENTS                                                                    VARCHAR2(4000)

SQL> select * from user_col_comments where table_name='T1';

TABLE_NAME                       COLUMN_NAME            COMMENTS

------------------------------ -------------------- --------------------

T1                               OWNER

T1                               TABLE_NAME            this is the name fo

    the table