Thursday, April 21, 2011

cursor oracle 10g

What is corsors in oracle
A cursors is a pointer used to fetch rows from a result set. One can think of a cursor as a data structure that describes the results returned from a SQL SELECT statement. One of the variables in this structure is a pointer to the next record to be fetched from the query results.

Two types of classification - I and II

I. Implicit and Explict

a. Implicit : More fast and less coding effort.

Will never raise INVALID_CURSOR error

Cannot be opened outside the statement

Raises NO_DATA_FOUND and TOO_MANY_ROWS exceptions (eg: select )

Implicit cursor returning more than one record? FOR LOOP cursors.

b. Explicit : 2 network round trips. Store data first then retrieve data. More programmatic control.

Programmer could open; fetch data, close, check attributes etc.

II Static and Dynamic

a. Static : Normal cursor (implicit or explicit)

b. Dynamic : Ref cursor: Cursor created only when it is opened.

Could be declared once and defined many times in different procedures.

Ref Cursors can have Record/s as return types. So could be used for returning

data to other languages like Java, C++ etc

II.b) Ref cursor - Two types

Strong : Ref cursor with a specified return type.

Weak : No return type specified.

3. Cursor attributes

%FOUND - records fetched successfully

%NOTFOUND - no records fetched

%ROWCOUNT - Number of records fetched

%ISOPEN - returns TRUE if cursor is open

Could be used for implicit and explicit cursors.



select * from emp -- also for delete operations


v_count:= SQL%ROWCOUNT

end if;


open c1; -- cursor c1 is select

fetch <>

exit when c1%NOTFOUND

Eg: Explicit cursor.


Cursor cur1 is

select ename,empno,sal from emp
where empno between 9000 and 1000
and sal<50000
and deptno=50
open cur1;
fetch cur1 into v_ename,v_empno,v_sal;
exit when cur1%notfound;
close cur1;

Key words :

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