How to populate a static junk dimension made of N boolean flags

Question

Hi, we want to populate a junk dimension (a table with N boolean fields - 18 in our case).
The records must contain all the possibile combinations of all the fields (with 18 integer fields whose value can be either 0 or 1, the number of possible combinations is 262144).
I'm looking for suggestions on how to do this (with a single SQL statement or with a cursor inside a procedure, they are both fine).
Thanks,
Andrea

Answer 1

You could use cross products/joins to achieve the result. Here is an example:
SQL> WITH boolean_flags AS
  2  (
  3          SELECT  0 AS FLG FROM DUAL UNION ALL
  4          SELECT  1 AS FLG FROM DUAL
  5  )
  6  SELECT  A.FLG
  7  ,       B.FLG
  8  ,       C.FLG
  9  FROM    BOOLEAN_FLAGS   A
10  ,       BOOLEAN_FLAGS   B
11  ,       BOOLEAN_FLAGS   C
12  /
       FLG        FLG        FLG
         0          0          0
         0          0          1
         0          1          0
         0          1          1
         1          0          0
         1          0          1
         1          1          0
         1          1          1If you need it to be more dynamic you can generate the SQL dynamically as shown below. This example would work for the number of columns ranging from 1-26 (I didn't do heavy testing):
SQL> VAR c REFCURSOR;
SQL>
SQL> DECLARE
  2          numDimensions   NUMBER  := 3;
  3          sqlText         VARCHAR2(4000) :='WITH boolean_flags AS
  4                                          (
  5                                                  SELECT  0 AS FLG FROM DUAL UNION ALL
  6                                                  SELECT  1 AS FLG FROM DUAL
  7                                          )
  8                                          SELECT A.FLG ';
  9          sqlFromText     VARCHAR2(4000) :='FROM BOOLEAN_FLAGS    A';
10  BEGIN
11          FOR i IN 2..numDimensions
12          LOOP
13                  sqlText := sqlText || ', ' || CHR(64+i) || '.FLG ';
14
15                  sqlFromText := sqlFromText || ', BOOLEAN_FLAGS ' || CHR(64+i);
16          END LOOP;
17
18          OPEN :c FOR sqlText || sqlFromText;
19  END;
20  /
PL/SQL procedure successfully completed.
SQL> PRINT C
       FLG        FLG        FLG
         0          0          0
         0          0          1
         0          1          0
         0          1          1
         1          0          0
         1          0          1
         1          1          0
         1          1          1
8 rows selected.Edited by: Centinul on Dec 28, 2009 9:35 AM