To do it interactively from SQL*PLUS:

desc my_table;


To do it in code:

set serveroutput on

declare x number;
begin
select count(*) into x from dba_tab_columns where table_name = 'My_Table_Name' and (column_name = 'ORDER_NUM' or column_name='DATE');
dbms_output.put_line(x);
end;
/


If the number output by X is the same as the number of columns you listed in the where clause above, they all exist. If X is less than the number of columns you listed, some of them don't exist.

Note: I used dbms_output.put_line solely to display the output for your use in SQL*PLUS. You could use this code in a procedure and test X with code rather than displaying it. Use capitals when searching the data dictionary for objects by name.

Is this what you wanted?