Oracle: Virtual columns vs DEFAULT values

A Oracle: Virtual columns vs DEFAULT values provides a value at query time:

create table tq84_virt_col_t (
   dt_start  date,
   dt_end    date,
   days      as ( dt_end - dt_start )
);


insert into tq84_virt_col_t(dt_start, dt_end) values (date '2022-03-05', date '2022-05-16');

select * from tq84_virt_col_t;

On the other hand, default values are used to provide a value in insert statements in absence of an explicitly given value:

create table tq84_def_col_t (
   id           number(5),
   default_val  date  default sysdate
);

insert into tq84_def_col_t (id) values (1);

select
   *
from
   tq84_def_col_t;

The expression that provides the value for a virtual column and default values can be queried from the column data_default in the data dictionary's view dba_tab_cols.

The value of virtual_column (YES or NO) determines if data_default is a default expression or not.

select
   obj.object_type,
   obj.owner,
   col.table_name,
   col.column_name,
   col.data_default,
   col.virtual_column,
   col.*
from
   dba_objects   obj                                          join
   dba_tab_cols  col  on obj.owner       = col.owner      and
                         obj.object_name = col.table_name
where
-- obj.oracle_maintained = 'N'                              and
   col.table_name in ('TQ84_VIRT_COL_T', 'TQ84_DEF_COL_T') and
   col.owner      = user
;