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?
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.
Explanation:
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)
Incorrect:
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.
Understand Invisible Columns