Set - 6

Question 21 :

What is a cursor?

Answer :

Oracle uses work area to execute SQL statements and store processing information PL/SQL construct called a cursor lets you name a work area and access its stored information A cursor is a mechanism used to fetch more than one row in a Pl/SQl block.


Question 22 :

What is the purpose of a cluster?

Answer :

Oracle does not allow a user to specifically locate tables, since that is a part of the function of the RDBMS. However, for the purpose of increasing performance, oracle allows a developer to create a CLUSTER. A CLUSTER provides a means for storing data from different tables together for faster retrieval than if the table placement were left to the RDBMS.
What is OCI. What are its uses?
Oracle Call Interface is a method of accesing database from a 3GL program. Uses--No precompiler is required,PL/SQL blocks are executed like other DML statements.
The OCI library provides
--functions to parse SQL statemets
--bind input variables
--bind output variables
--execute statements
--fetch the results


Question 23 :

How you open and close a cursor variable. Why it is required?

Answer :

OPEN cursor variable FOR SELECT...Statement
CLOSE cursor variable In order to associate a cursor variable with a particular SELECT statement OPEN syntax is used. In order to free the resources used for the query CLOSE statement is used.
Display Odd/ Even number of records?
Odd number of records:
select * from emp where (rowid,1) in (select rowid, mod(rownum,2) from emp);
Output:-
1
3
5
Even number of records:
select * from emp where (rowid,0) in (select rowid, mod(rownum,2) from emp)
Output:-
2
4
6


Question 24 :

What are various constraints used in SQL?

Answer :

-NULL
-NOT NULL
-CHECK
-DEFAULT


Question 25 :

Can cursor variables be stored in PL/SQL tables. If yes how. If not why?

Answer :

No, a cursor variable points a row which cannot be stored in a two-dimensional PL/SQL table.