Selecting rows as columns

Question

Hi,
I've got a challenge. I need to select row data as columns.
Suppose, I have this:
CREATE TABLE master
  id NUMBER,
  name VARCHAR2(50),
  CONSTRAINT pk_master PRIMARY KEY(id) 
CREATE TABLE detail
  id NUMBER,
  master_id,
  type VARCHAR2(10),
  value NUMBER,
  CONSTRAINT pk_detail PRIMARY KEY(id),
  CONSTRAINT fk_master FOREIGN KEY(master_id)
       REFERENCES master(id),
  CONSTRAINT c_type CHECK (type IN ('apple','orange'))
);Now, suppose master and detail holds the following data:
Master:
ID  NAME
1   Jill
2   Jack
Detail:
ID  MASTER_ID TYPE      VALUE
1   1         apple     120
2   1         orange    230
3   2         apple     10Here comes the challenge: what do I have to put in a selectstatement, to get this result:
NAME    APPLE    ORANGE
Jill    120      230
Jack    10I know what types there are up front (only apple and orrange), so the query may use that knowledge.
Bonus guru points however to the one who can make a generic query that can convert the type rows into columns generically, regardless of what and how many types there are.

Answer 1

scott@ORA92> -- test data:
scott@ORA92> SELECT * FROM master
  2  /
        ID NAME
         1 Jill
         2 Jack
scott@ORA92> SELECT * FROM detail
  2  /
        ID  MASTER_ID TYPE            VALUE
         1          1 apple             120
         2          1 orange            230
         3          2 apple              10
scott@ORA92> -- PL/SQL for any number of values of type (apple, orange, etc.):
scott@ORA92> VARIABLE g_ref REFCURSOR
scott@ORA92> DECLARE
  2    v_sql VARCHAR2(32767);
  3  BEGIN
  4    v_sql := 'SELECT master.name';
  5    FOR rec IN (SELECT DISTINCT type FROM detail) LOOP
  6        v_sql := v_sql
  7        || ',SUM(DECODE(type,''' || rec.type || ''',value)) ' || rec.type;
  8    END LOOP;
  9    v_sql := v_sql
10    || ' FROM   master, detail'
11    || ' WHERE  master.id = detail.master_id'
12    || ' GROUP  BY master.name';
13    OPEN :g_ref FOR v_sql;
14  END;
15  /
PL/SQL procedure successfully completed.
scott@ORA92> PRINT g_ref
NAME                                                    APPLE     ORANGE
Jack                                                       10
Jill                                                      120        230
scott@ORA92>