PLSQL: edit cursor at runtime - plsql

Question

I'm a bit confused
is it possible in a function/proc something like this?
CURSOR CR IS
SELECT
FROM
WHERE Y = X
and later in the body, change the X value into Z or something else, and then re-open the cursor so it fetches the rows with the Y = Z?

Answer 1

There are a couple of ways to do this without resorting to dynamic SQL. One option would be to use a parameterized cursor:
DECLARE
nSome_value NUMBER := 666;
CURSOR CR(parmSome_value NUMBER) IS
SELECT *
FROM SOME_TABLE
WHERE SOME_COLUMN = parmSome_value;
BEGIN
nSome_value := 123; -- change value of nSome_value
OPEN CR(nSome_value); -- pass nSome_value in as the value of the cursor parameter
-- Fetch from the cursor, do whatever
CLOSE CR;
END;
It's still static SQL but by passing a parameter to the cursor you increase the reusability of the cursor.
Another option is to use a cursor FOR loop, referencing the variable in the loop's SQL:
DECLARE
nSome_value NUMBER := 666;
BEGIN
nSome_value := 123; -- change value of nSome_value
FOR aRow IN (SELECT *
FROM SOME_TABLE
WHERE SOME_COLUMN = nSome_value)
BEGIN
-- Do something useful with the rows returned by the cursor
END LOOP;
END;
Note that in these cases you're not changing the SQL - you're just changing the values of the variable or parameter used in the query. One advantage of these approaches is that unlike dynamically generated SQL they're not vulnerable to SQL injection attacks.
Share and enjoy.

Answer 2

Yes, try something like this (typed quickly so syntax might not be exact)
sql VARCHAR2(255);
cur REF CURSOR;
val varchar2(100);
val := X;
sql := 'SELECT .. FROM .. WHERE Y = :val';
open cur for
sql
USING val;
close cur;
....
val := Z;
open cur for
sql
USING val;

Answer 3

This can also be done by using a subprograms like function instead of using a cursor as it
wil shorten the code :
create or replace function getashish(dept varchar2) return emp3 as
emp5 emp3 := emp3();
str varchar2(300);
begin
str := 'select emp1(e.last_name,l.city,e.salary) from employees e join departments d
on e.department_id = d.department_id join locations l on d.location_id=l.location_id where
d.department_name = :dept';
execute immediate str
bulk collect into emp5
using dept;
return emp5;
end;
here you have to create a object including the return types yoy want in the return and then create and table of that object:
create or replace type emp1 as object (lname varchar2(10),city varchar2(10),sal number(10));
and
CREATE OR REPLACE
type emp3 as table of emp1;