Recursion cursor

Question

I have two tables
course (cname,courno) and prerequsite(courseno,prerequisite)
prerequsite is foreign key on course
on pl/sql
a course will be input and all prerequsite course and prerequsite of prerequsite course will be fetch into a table
so how can i write this code
I tried to use cursor but one cursor is not necessary, is there a recursion cursor
I mean u can get one prerequisite but u can not get prerequisite of prerequisite in that cursor
Thnaks in advance

Answer 1

You need an hierarchical query here on the prerequisites table to give you the list. If you want course names for all the prerequisites, then you will need to also join to courses a seconf time as im my example.
SQL> SELECT * FROM courses
  2  /
  COURSENO CNAME
       301 MEDIUM MATH
       201 EASIER MATH
       101 BASIC MATH
       305 MULTIPLICATION
       205 SUBTRACTION
       105 ADDITION
       402 HARDER MATH
       401 HARD MATH
       406 HARD ENGLISH
SQL> SELECT * FROM prerequisite
  2  /
  COURSENO PREREQUISITE
       401          301
       301          201
       201          101
       401          305
       305          205
       205          105
       402          301
       402          306
SQL> SELECT a.courseno course, a.cname course_name,b.prerequisite,
  2         c.cname prerequisite_name
  3  FROM courses a,
  4       (SELECT courseno,prerequisite
  5        FROM prerequisite
  6        START WITH courseno = 401
  7        CONNECT BY PRIOR prerequisite = courseno) b,
  8        courses c
  9  WHERE a.courseno = b.courseno and
10        b.prerequisite = c.courseno
11  /
    COURSE COURSE_NAME          PREREQUISITE PREREQUISITE_NAME
       201 EASIER MATH                   101 BASIC MATH
       205 SUBTRACTION                   105 ADDITION
       301 MEDIUM MATH                   201 EASIER MATH
       305 MULTIPLICATION                205 SUBTRACTION
       401 HARD MATH                     301 MEDIUM MATH
       401 HARD MATH                     305 MULTIPLICATIONJohn