Looking for SQL to Display Rows as Columns in a View

Question

Hi!
I am using Oracle 10g (10.1.0.4.0) 64 bit on Red Hat Enterprise Linux AS release 3.
I have the following tables:
Table A
A_ID number (primary key)
Table B
B_ID number (primary key)
B_NAME varchar2
B_DESC varchar2
Table C
C_ID number (primary key)
B_ID number (foreign key to table B)
A_ID number (foreign key to table A)
ORDERING number
A row in table A can have from 0 (zero) to 3 (three) rows in table C associated with it.
I am trying to make a view that displays A.A_ID and its associated rows from table C as a single row. For example, the following query:
select A.A_ID, C.B_ID, B.B_NAME, B.B_DESC, C.ORDERING
  from C, B, A
where C.A_ID = A.A_ID
   and C.B_ID = B.B_IDYields the following results:
A_ID B_ID B_NAME B_DESC ORDERING
100   10 A      One    1
100   20 B      Two    2
100   30 C      Three  3I would like to get the following:
A_ID B_NAME_1 B_NAME_2 B_NAME_3
100 A        B        CThanks (in advance :-),
Avi.

Answer 1

SQL> CREATE TABLE dt_test_a(a_id number)
  2  /
Table created.
SQL> CREATE TABLE dt_test_b(b_id number, b_name varchar2(1),b_desc varchar2(10))
  2  /
Table created.
SQL> CREATE TABLE dt_test_c(c_id number, b_id number, a_id number, ordering number)
  2  /
Table created.
SQL>
SQL> insert into dt_test_a values(100)
  2  /
1 row created.
SQL> insert into dt_test_b values(10, 'A','One')
  2  /
1 row created.
SQL> insert into dt_test_b values(20, 'B','Two')
  2  /
1 row created.
SQL> insert into dt_test_b values(30, 'C','Three')
  2  /
1 row created.
SQL> insert into dt_test_c values(1, 10, 100, 1)
  2  /
1 row created.
SQL> insert into dt_test_c values(2, 20, 100, 2)
  2  /
1 row created.
SQL> insert into dt_test_c values(3, 30, 100, 3)
  2  /
1 row created.
SQL>
SQL> SELECT
  2     a.a_id,
  3     DECODE(c.ordering, 1, b.b_name) b_name_1,
  4     DECODE(c.ordering, 2, b.b_name) b_name_2,
  5     DECODE(c.ordering, 3, b.b_name) b_name_3
  6  FROM
  7     dt_test_a a,
  8     dt_test_b b,
  9     dt_test_c c
10  WHERE
11     a.a_id = c.a_id
12  AND
13     b.b_id = c.b_id
14  /
     A_ID B B B
      100 A
      100   B
      100     C
SQL>
SQL> SELECT
  2     a.a_id,
  3     MAX(DECODE(c.ordering, 1, b.b_name)) b_name_1,
  4     MAX(DECODE(c.ordering, 2, b.b_name)) b_name_2,
  5     MAX(DECODE(c.ordering, 3, b.b_name)) b_name_3
  6  FROM
  7     dt_test_a a,
  8     dt_test_b b,
  9     dt_test_c c
10  WHERE
11     a.a_id = c.a_id
12  AND
13     b.b_id = c.b_id
14  GROUP BY
15     a.a_id
16  /
     A_ID B B B
      100 A B C
SQL>
SQL>
SQL> insert into dt_test_a values(200)
  2  /
1 row created.
SQL> insert into dt_test_b values(40, 'A','One')
  2  /
1 row created.
SQL> insert into dt_test_b values(50, 'B','Two')
  2  /
1 row created.
SQL> insert into dt_test_b values(60, 'C','Three')
  2  /
1 row created.
SQL> insert into dt_test_c values(4, 40, 200, 3)
  2  /
1 row created.
SQL> insert into dt_test_c values(5, 50, 200, 2)
  2  /
1 row created.
SQL> insert into dt_test_c values(6, 60, 200, 1)
  2  /
1 row created.
SQL>
SQL> SELECT
  2     a.a_id,
  3     MAX(DECODE(c.ordering, 1, b.b_name)) b_name_1,
  4     MAX(DECODE(c.ordering, 2, b.b_name)) b_name_2,
  5     MAX(DECODE(c.ordering, 3, b.b_name)) b_name_3
  6  FROM
  7     dt_test_a a,
  8     dt_test_b b,
  9     dt_test_c c
10  WHERE
11     a.a_id = c.a_id
12  AND
13     b.b_id = c.b_id
14  GROUP BY
15     a.a_id
16  /
     A_ID B B B
      100 A B C
      200 C B A