Examine the following command:
CREATE TABLE (prod_id number (4),
Prod_name varchar2 (20),
Category_id number (30),
Quantity_on_hand number (3) INVISIBLE);
Which three statements are true about using an invisible column in the PRODUCTS table? (Choose three.)
A . The %ROWTYPE attribute declarations in PL/SQL to access a row will not display the invisible column in the output.
B . The DESCRIBE commands in SQL *Plus will not display the invisible column in the output.
C . Referential integrity constraint cannot be set on the invisible column.
D . The invisible column cannot be made visible and can only be marked as unused.
E . A primary key constraint can be added on the invisible column.
AB: You can make individual table columns invisible. Any generic access of a table does not show the invisible columns in the table.
For example, the following operations do not display invisible columns in the output:
* SELECT * FROM statements in SQL
* DESCRIBE commands in SQL*Plus
* %ROWTYPE attribute declarations in PL/SQL
* Describes in Oracle Call Interface (OCI)
Not D: You can make invisible columns visible.
You can make a column invisible during table creation or when you add a column to a table, and you can later alter the table to make the same column visible.