CODEWITHSUNDEEP
sqloracle-databaseplsql
Coilin
Coilin

Reputation: 23

Is there a way to select several rows by using parameters?

I am trying to write a code which can find all possible routes from a graph table. The code should be worked by using a single input value. E.g. I want to find all possible routes from point A to Point B.

I think that a procedure can maybe solve the problem, but I get the error message.

The graph tabel (a overview of all routes) is

P_FROM      P_TO     DISTANCE
A           B         4
A           C         7
B           C        10
C           D        15
B           D        17
A           D        23
B           E        22
C           E        29

and the procedure is

CREATE OR REPLACE PROCEDURE p_find_all_routes (
   p_start   IN VARCHAR2 DEFAULT '%',
   p_end     IN VARCHAR2 DEFAULT '%',
   p_via     IN VARCHAR2 DEFAULT '%')
AS
BEGIN
   -- =======================================================================
   -- Author:       Coilin P. Boylan Jeritslev (CTBJ)
   -- Description:   Find all possible routes between two different points
   -- "p_start" and "p_end" via the choosen point "p_via" in a graph-tabel.
   -- =======================================================================

   WITH multiroutes (p_from, p_to, full_route, total_distance)
        AS (SELECT p_from,
                   p_to,
                   p_from || '->' || p_to full_route,
                   distance total_distance
              FROM graph
             WHERE p_from LIKE p_start
            UNION ALL
            SELECT M.p_from,
                   n.p_to,
                   M.full_route || '->' || n.p_to full_route,
                   M.total_distance + n.distance total_distance
              FROM multiroutes M JOIN graph n ON M.p_to = n.p_from
             WHERE n.p_to <> ALL (M.full_route))
     SELECT *
       FROM multiroutes
      WHERE     p_to LIKE p_end
            AND (   full_route LIKE ('%->' || p_via || '%')
                 OR full_route LIKE ('%' || p_via || '->%'))
   ORDER BY p_from, p_to, total_distance ASC;
END;
/

When I'm executing the procedure with the following inputs:

EXEC p_find_all_routes('A','E','%')

I expect, the procedure is compiled and I get the result

P_FROM    P_TO     FULL_ROUTE     TOTAL_DISTANCE
A         E        A->B->E        26
A         E        A->C->E        36
A         E        A->B->C->E     43

But I get the PLS-00428 error message. Something about INTO.

I don't want to insert output values into a tabel. I want just to see the output values. How can I do it?

Upvotes: 2

Views: 68

Answers (1)

Ankit Bajpai
Ankit Bajpai

Reputation: 13509

You cannot return the result set in Oracle by using only Query. You need to use Ref cursor for the same. You can try below code - 

CREATE OR REPLACE PROCEDURE p_find_all_routes (
   p_start   IN VARCHAR2 DEFAULT '%',
   p_end     IN VARCHAR2 DEFAULT '%',
   p_via     IN VARCHAR2 DEFAULT '%',
   multiroutes OUT SYS_REFCURSOR)
AS
BEGIN
   -- =======================================================================
   -- Author:       Coilin P. Boylan Jeritslev (CTBJ)
   -- Description:   Find all possible routes between two different points
   -- "p_start" and "p_end" via the choosen point "p_via" in a graph-tabel.
   -- =======================================================================
OPEN multiroutes FOR
   WITH multiroutes (p_from, p_to, full_route, total_distance)
        AS (SELECT p_from,
                   p_to,
                   p_from || '->' || p_to full_route,
                   distance total_distance
              FROM graph
             WHERE p_from LIKE p_start
            UNION ALL
            SELECT M.p_from,
                   n.p_to,
                   M.full_route || '->' || n.p_to full_route,
                   M.total_distance + n.distance total_distance
              FROM multiroutes M JOIN graph n ON M.p_to = n.p_from
             WHERE n.p_to <> ALL (M.full_route))
     SELECT *
       FROM multiroutes
      WHERE     p_to LIKE p_end
            AND (   full_route LIKE ('%->' || p_via || '%')
                 OR full_route LIKE ('%' || p_via || '->%'))
   ORDER BY p_from, p_to, total_distance ASC;
END;
/

You can then call this procedure later by declaring Ref cursor variable.

DECLARE
    Result SYS_REFCURSOR;
BEGIN
    p_find_all_routes('A','E','%', Result);
END;

Upvotes: 2

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