有没有一种方法可以通过使用参数来选择几行? [英] Is there a way to select several rows by using parameters?

问题描述

我正在尝试编写一个代码，该代码可以从图形表中找到所有可能的路线.该代码应通过使用单个输入值来工作.例如.我想找到从A点到B点的所有可能路线.

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.

我认为某个过程也许可以解决问题，但是我得到了错误消息.

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

图形表格(所有路线的概述)为

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

过程是

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;
/

当我使用以下输入执行过程时:

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

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

我希望程序已编译并得到结果

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

但是我收到PLS-00428错误消息.关于INTO.

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

我不想将输出值插入表格.我只想查看输出值.我该怎么办?

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

推荐答案

您不能仅使用查询在Oracle中返回结果集.您需要使用Ref光标.您可以尝试以下代码-

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;
/

随后您可以通过声明Ref游标变量来调用此过程.

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; 

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