Examine the following command: Which three statements are true about using an invisible
column in the PRODUCTS table?
A.
Referential integrity constraint cannot be set on the invisible column.
B.
The invisible column cannot be made visible and can only be marked as unused.
C.
The %ROWTYPE attribute declarations in PL/SQL to access a row will not display the
invisible column in the output.
D.
The DESCRIBE commands in SQL *Plus will not display the invisible column in the
output.
E.
A primary key constraint can be added on the invisible column.
C.
The %ROWTYPE attribute declarations in PL/SQL to access a row will not display the
invisible column in the output.
D.
The DESCRIBE commands in SQL *Plus will not display the invisible column in the
output.
E.
A primary key constraint can be added on the invisible column.
SQL> CREATE TABLE my_test (prod_id number(4),
Prod_name varchar2 (20),
Category_id number(30),
Quantity_on_hand number (3) INVISIBLE); 2 3 4
Table created.
SQL> create table my_test2 (a number primary key);
Table created.
–DESCRIBE
SQL> desc my_test
Name Null? Type
—————————————– ——– —————————-
PROD_ID NUMBER(4)
PROD_NAME VARCHAR2(20)
CATEGORY_ID NUMBER(30)
–PRIMARY KEY
SQL> alter table my_test add primary key(Quantity_on_hand);
Table altered.
–FOREIGN KEY
SQL> alter table my_test add foreign key(Quantity_on_hand) referencing my_test2(a);
Table altered.
–%ROWTYPE
SQL> declare
rec_my_test mu_test%rowtype;
begin
dbms_output.put_line(rec_my_test.Quantity_on_hand);
end;
/ 2 3 4 5 6
dbms_output.put_line(rec_my_test.Quantity_on_hand);
*
ERROR at line 4:
ORA-06550: line 4, column 34:
PLS-00302: component ‘QUANTITY_ON_HAND’ must be declared
ORA-06550: line 4, column 1:
PL/SQL: Statement ignored