create or replace table A (i integer, j integer, value float );
insert into A values
  (1, 1, 1),
  (1, 2, 2),
  (1, 3, 3),
  (2, 1, 2),
  (2, 2, 5),
  (2, 3, 7);

create or replace table B (i integer, j integer, value float );
insert into B values
  (1, 1, 2),
  (1, 2, 4),
  (1, 3, 8),
  (2, 1, 1),
  (2, 2, 5),
  (2, 3, -10),
  (3, 1, 3),
  (3, 2, 6),
  (3, 3, 9);

.print Display A in a matrix format including the row id
pivot A on j using max(value) order by i;

.print Display B likewise
pivot B on j using max(value) order by i;

. print Compute C = A * B
CREATE OR REPLACE table C as
  SELECT A.i, B.j,
       SUM(A.value * B.value) AS value
  FROM A INNER JOIN B
  ON A.j = B.i
  GROUP BY A.i, B.j;

.print Display C in matrix format excluding the row id
select columns(* exclude (i))
  from (pivot C on j using max(value))
  order by i;