Running queries against cursor results?

Question

I'm running a cursor in a stored procedure, and the query itself is dependent on one of the parameters passed to the SP. So, for example:
create procedure annoying as
SQLString varchar2(50);
myCursor Types.cursorType; -- defined elsewhere in pkg.
begin
if parameter = 1 then SQLString = "select x,y from table1";
if parameter = 2 then SQLString = "select x,z from table2";
open myCursor for SQLString;
At this point, I need to run a further query against the result set from the cursor. I have no clue how to proceed with this. Am I barking up the wrong tree? Should I be looking for a different solution?

Answer 1

Instead of looping through a cursor and comparing the values of x, use the entire select statement that you would have used for the cursor as an inline view (select statement in the from clause) in your subsequent cursor and join via x. Please see the example below. You can continue this nesting for as many levels as required. For example, instead of opening the ref cursor for sqlstring2, you could use that as an inline view in another sqlstring3 and open the ref cursor for sqlstring3.
scott@ORA92> create or replace package types
  2  as
  3    type cursortype is ref cursor;
  4  end types;
  5  /
Package created.
scott@ORA92> show errors
No errors.
scott@ORA92> create or replace procedure annoying
  2    (parameter in  number,
  3       myCursor  out Types.cursortype)
  4  as
  5    SQLString  varchar2(50);
  6    sqlString2 varchar2(4000);
  7  begin
  8    if parameter = 1 then SQLString := 'select deptno x, dname y from dept';
  9    elsif parameter = 2 then SQLString := 'select deptno x,loc z from dept';
10    end if;
11    sqlstring2 := 'select e.empno, d.*
12                  from   emp e,
13                      (' || sqlstring || ') d -- inline view
14                  where e.deptno = d.x';
15    open myCursor for SQLString2;
16  end annoying;
17  /
Procedure created.
scott@ORA92> show errors
No errors.
scott@ORA92> variable g_ref refcursor
scott@ORA92> execute annoying (1, :g_ref)
PL/SQL procedure successfully completed.
scott@ORA92> print g_ref
     EMPNO          X Y
      7934         10 ACCOUNTING
      7839         10 ACCOUNTING
      7782         10 ACCOUNTING
      7902         20 RESEARCH
      7876         20 RESEARCH
      7788         20 RESEARCH
      7566         20 RESEARCH
      7369         20 RESEARCH
      7900         30 SALES
      7844         30 SALES
      7698         30 SALES
      7654         30 SALES
      7521         30 SALES
      7499         30 SALES
14 rows selected.
scott@ORA92> execute annoying (2, :g_ref)
PL/SQL procedure successfully completed.
scott@ORA92> print g_ref
     EMPNO          X Z
      7934         10 NEW YORK
      7839         10 NEW YORK
      7782         10 NEW YORK
      7902         20 DALLAS
      7876         20 DALLAS
      7788         20 DALLAS
      7566         20 DALLAS
      7369         20 DALLAS
      7900         30 CHICAGO
      7844         30 CHICAGO
      7698         30 CHICAGO
      7654         30 CHICAGO
      7521         30 CHICAGO
      7499         30 CHICAGO
14 rows selected.