How to open multiple cursors with main cursor data

Question

I am trying to read a cursor in a stored procedure returned from another stored procedure and want to write to multiple out cursors by looping through main cursor data.

-- TYPE myCursorType IS REF CURSOR;
PROCEDURE prcgetalldetails (
    incustomernumber    IN customer.customer_number%TYPE,
    accountdetailscur   OUT pkgaccount.curaccountdetailstype,
    fundscur            OUT mycursortype,
    otherdetailscur     OUT mycursortype
) IS
    localaccountdetails   pkgaccount.curinvestmentaccount;
    outcfunds             curinvestmentaccount;
    accountdetails        pkgaccount.curaccountdetailstype%rowtype;
BEGIN
    pkgaccount.accountdetails(incustomernumber,localaccountdetails);
    LOOP
        FETCH localaccountdetails INTO accountdetails;
        EXIT WHEN localaccountdetails%notfound;
        dbms_output.put_line(localaccountdetails.accountname
         || ','
         || localaccountdetails.accountnumber);
        
        -- I have to return the 'accountdetailscur' as well,before that I have to loop through it and return remaining data as well
        -- Based on account number I have to execute other queries and fetch other details and give those cursors back
        OPEN fundscur FOR
            SELECT
                fundname,
                fundid,
                fundbalance
            FROM
                fundstable
            WHERE
                accountnumber = localaccountdetails.accountnumber;

        OPEN otherdetailscur FOR
            SELECT
                col1,
                col2
            FROM
                othertable
            WHERE
                accountnumber = localaccountdetails.accountnumber;

    END LOOP;

END;

As I am opening cursor in loop, it will return only last row details of localaccountdetails cursor. I am not sure how to use BUILK COLLECT to collect everything and loop on top of it.

And I don't know how to return the localaccountdetails as OUT data & loop it to get remaining data.

Answer 1

You can nest one cursor within another with a cursor expression. This is of the form:

select cursor ( select ... ) from ...

So you can do something like this:

create table par ( pk primary key ) as 
  select level pk
  from   dual
  connect by level <= 5;
  
create table chd as 
  select r.c1 pk, par.pk fk 
  from   par, lateral ( 
    select level c1 from dual
    connect by level <= pk
  ) r;
  
select pk,
       cursor (
         select * from chd c
         where  par.pk = c.fk
       )
from   par;

declare
  cursor cur is 
    select pk,
           cursor (
             select * from chd c
             where  par.pk = c.fk
           )
    from   par;
  
  pk      integer;
  chd_cur sys_refcursor;
  type chd_arr is table of chd%rowtype
    index by pls_integer;
  chd_recs chd_arr;
begin
  open cur;
  loop
    fetch cur into pk, chd_cur;
    exit when cur%notfound;
    
    fetch chd_cur bulk collect into chd_recs;
    dbms_output.put_line ( 
      'Fetched ' || pk || ' child rows ' || chd_recs.count 
    );
  end loop;
  close cur;
end;
/

Fetched 1 child rows 1
Fetched 2 child rows 2
Fetched 3 child rows 3
Fetched 4 child rows 4
Fetched 5 child rows 5

Note that this means you're rolling your own nested loops join. Unless you really need to control how many rows the client fetches from the child/inner table, I'd make this a join.

You can aggregate the inner table's rows into JSON or a nested table if you want to ensure you get one row from the parent table, e.g.:

select par.pk,
       json_arrayagg ( 
         json_object ( chd.* ) 
       )
from   par
join   chd
on     par.pk = chd.fk
group  by par.pk;

PK    JSON_ARRAYAGG(JSON_OBJECT(CHD.*))                                                   
    1 [{"PK":1,"FK":1}]                                                                    
    2 [{"PK":1,"FK":2},{"PK":2,"FK":2}]                                                    
    3 [{"PK":1,"FK":3},{"PK":3,"FK":3},{"PK":2,"FK":3}]                                    
    4 [{"PK":1,"FK":4},{"PK":4,"FK":4},{"PK":3,"FK":4},{"PK":2,"FK":4}]                    
    5 [{"PK":1,"FK":5},{"PK":5,"FK":5},{"PK":4,"FK":5},{"PK":3,"FK":5},{"PK":2,"FK":5}]