Set - 4

Question 16 :

If unique key constraint on DATE column is created, will it validate the rows that are inserted with SYSDATE?

Answer :

It won't, Because SYSDATE format contains time attached with it.


Question 17 :

What is a database link?

Answer :

Database link is a named path through which a remote database can be accessed.


Question 18 :

How to access the current value and next value from a sequence? Is it possible to access the current value in a session before accessing next value?

Answer :

Sequence name CURRVAL, sequence name NEXTVAL. It is not possible. Only if you access next value in the session, current value can be accessed.


Question 19 :

What is CYCLE/NO CYCLE in a Sequence?

Answer :

CYCLE specifies that the sequence continue to generate values after reaching either maximum or minimum value. After pan-ascending sequence reaches its maximum value, it generates its minimum value. After a descending sequence reaches its minimum, it generates its maximum.
NO CYCLE specifies that the sequence cannot generate more values after reaching its maximum or minimum value.


Question 20 :

What are the advantages of VIEW?

Answer :

- To protect some of the columns of a table from other users.
- To hide complexity of a query.
- To hide complexity of calculations.