Session Notes - 
Cursor is a memory area in which a SQL Query is processed and results are cached.
Explicit/Implicit Cursors
Steps - DECLARE, OPEN, FETCH UNTIL ALL ROWS ARE FETCHED AND THEN CLOSE.
Four attributes - ISOPEN, NOTFOUND, FOUND, ROWCOUNT
CURSOR FOR LOOPS
	DECLARE
	USING A FOR LOOP - YOU CAN OPEN, FETCH AND CLOSE (UNTIL END LOOP).

USAGE OF FOR UPDATE CLAUSE

CURSOR WITH PARAMETER
	CURSOR C1 
	(A1 VARCHAR, A2 VARCHAR)
	IS
	SELECT * FROM EMP
	WHERE ENAME LIKE A1 OR DNAME LIKE A2;
BEGIN

	OPEN C1('BOB', 'ACCOUNTING);
	...
	CLOSE C1;
	OPEN C1('SALLY', 'HR);
	...
	CLOSE C1;
END;

Doing a select for update  allows selection of data rows --> locked for update.

Slow down the overall system.

When updating exiting values in row --> useful.

CURSOR c1 is
	select empno, ename, deptno
	from emp
	where sal > 2000
	for update of dept nowait;

Open --> Fetch rows in a loop - 
Point to current cursor --> WHERE current of c1; <-- explicit reference to rowid.

BEGIN
	FOR emp_rec in c1
	loop
		if emp_rec dept in (10,20) then
			update emp set deptno = 40
			where current of c1;
		end if;
	end loop;
END;
/

When a cursor is created with a subquery - explicit reference is given only to the outer cursor and not the internal cursor.

Working with Exceptions:
 Block of code -- Problem occurs in code. --> Exception is thrown - ctrl of code block in send to Exception Block (Exception can be either be managed or reset).

Between Begin and End clause exception can occur.
Two type of exceptions can occur
	Oracle error - system errors.
	Custom exception - for application - user-defined.


Pre-defined exceptions are implicitly raised. (20)
Non Pre-defined exceptions 
User-defined exceptions are explicily raised.


EXCEPTION
	WHEN exception1 then 
	statements
	..
	when exception2 then

	when others then
end;
/

NO DATA FOUND
TOO_MANY_ROWS
non pre-defined exception
declare
	myexception EXCEPTION;
	PRAGMA_EXCEPTION_INIT(myexception, -1133);
begin
	....
exception
	when myexception then
	dbms_output.put_line('error');

end;
/


user-defined exception;

declare
	myexception EXCEPTION;
begin
	...
	if sql%notfound then
		raise myexception;
	end if

exception
	when myexception then
	dbms_output.put_line('error');

end;
/

raise_application_error(-222222, 'error message');
--used in exception block or begin block.