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Working with more than one cursor - Oracle

This is part 11 of a series of articles focusing on database interactions with Oracle PL/SQL. In my previous article, I introduced the concept of the explicit cursor and looked at several approaches for using the explicit cursors. In this article, we shall delve more deeply into explicit cursors.

TABLE OF CONTENTS:
  1. Database Interaction with PL/SQL: Explict Cursors in Depth
  2. Working with more than one cursor
  3. How the program works
  4. Further approaches to the above program
  5. Cursors with parameters a complicated example
  6. Can we use JOINS in cursors?
By: Jagadish Chatarji
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August 02, 2005

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We can work with more than one cursor at a time by using nested loops. Let us consider the following example:

declare

  cursor c_emp is

        select ename,deptno from emp;

  cursor c_dept is

        select deptno,dname from dept;

  r_emp c_emp%rowtype;

  r_dept      c_dept%rowtype;

begin

  open c_dept;

  loop

        fetch c_dept into r_dept;

        exit when c_dept%notfound;

dbms_output.put_line('-----------------');

        dbms_output.put_line(r_dept.dname);

        dbms_output.put_line('-----------------');

        open c_emp;

        loop

              fetch c_emp into r_emp;

              exit when c_emp%notfound;

              if r_emp.deptno = r_dept.deptno then

                    dbms_output.put_line(r_emp.ename);

              end if;

        end loop;

        close c_emp;

  end loop;

  close c_dept;

end;

 

Before discussing such a lengthy program, let us see the output of above program:

-----------------
ACCOUNTING
-----------------
KING
CLARK
MILLER
-----------------
RESEARCH
-----------------
JONES
FORD

And so on. It displays all employees separated and categorized under department names. The next section explains the above program in a great deal of detail.



 
 
>>> More Oracle Articles          >>> More By Jagadish Chatarji
 

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