Oracle cursors,Types of cursors

1. REF CURSORS AND CURSOR VARIABLES
1 This is unconstrained cursor which will return different types depends
upon the user input.
2 Ref cursors can not be closed implicitly.
3 Ref cursor with return type is called strong cursor.
4 Ref cursor with out return type is called weak cursor.
5 You can declare ref cursor type in package spec as well as body.
6 You can declare ref cursor types in local subprograms or anonymous
blocks.
7 Cursor variables can be assigned from one to another.
8 You can declare a cursor variable in one scope and assign another
cursor variable with different scope, then you can use the cursor
variable even though the assigned cursor variable goes out of scope.
9 Cursor variables can be passed as a parameters to the subprograms.
10 Cursor variables modes are in or out or in out.
11 Cursor variables can not be declared in package spec and package
body (excluding subprograms).
12 You can not user remote procedure calls to pass cursor variables from
one server to another.
13 Cursor variables can not use for update clause.
14 You can not assign nulls to cursor variables.
15 You can not compare cursor variables for equality, inequality and
nullity.
Ex:
CREATE OR REPLACE PROCEDURE REF_CURSOR(TABLE_NAME IN VARCHAR) IS
type t is ref cursor;
c t;
v_dept dept%rowtype;
type r is record(ename emp.ename%type,job emp.job%type,sal
emp.sal%type);
v_emp r;
v_stud student.name%type;
BEGIN
if table_name = 'DEPT' then
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2. open c for select * from dept;
elsif table_name = 'EMP' then
open c for select ename,job,sal from emp;
elsif table_name = 'STUDENT' then
open c for select name from student;
end if;
loop
if table_name = 'DEPT' then
fetch c into v_dept;
exit when c%notfound;
dbms_output.put_line('Deptno = ' || v_dept.deptno || ' Dname
= ' ||
v_dept.dname || ' Loc = ' ||
v_dept.loc);
elsif table_name = 'EMP' then
fetch c into v_emp;
exit when c%notfound;
dbms_output.put_line('Ename = ' || v_emp.ename || ' Job = '
|| v_emp.job
|| ' Sal = ' || v_emp.sal);
elsif table_name = 'STUDENT' then
fetch c into v_stud;
exit when c%notfound;
dbms_output.put_line('Name = ' || v_stud);
end if;
end loop;
close c;
END;
Output:
SQL> exec ref_cursor('DEPT')
Deptno = 10 Dname = ACCOUNTING Loc = NEW YORK
Deptno = 20 Dname = RESEARCH Loc = DALLAS
Deptno = 30 Dname = SALES Loc = CHICAGO
Deptno = 40 Dname = OPERATIONS Loc = BOSTON
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3. SQL> exec ref_cursor('EMP')
Ename = SMITH Job = CLERK Sal = 800
Ename = ALLEN Job = SALESMAN Sal = 1600
Ename = WARD Job = SALESMAN Sal = 1250
Ename = JONES Job = MANAGER Sal = 2975
Ename = MARTIN Job = SALESMAN Sal = 1250
Ename = BLAKE Job = MANAGER Sal = 2850
Ename = CLARK Job = MANAGER Sal = 2450
Ename = SCOTT Job = ANALYST Sal = 3000
Ename = KING Job = PRESIDENT Sal = 5000
Ename = TURNER Job = SALESMAN Sal = 1500
Ename = ADAMS Job = CLERK Sal = 1100
Ename = JAMES Job = CLERK Sal = 950
Ename = FORD Job = ANALYST Sal = 3000
Ename = MILLER Job = CLERK Sal = 1300
SQL> exec ref_cursor('STUDENT')
Name = saketh
Name = srinu
Name = satish
Name = sudha
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