--setup
CREATE TABLE averages (val INTEGER);
INSERT INTO averages VALUES (1);
INSERT INTO averages VALUES (2);
INSERT INTO averages VALUES (3);
INSERT INTO averages VALUES (4);
INSERT INTO averages VALUES (5);
INSERT INTO averages VALUES (6);
INSERT INTO averages VALUES (7);
INSERT INTO averages VALUES (8);
INSERT INTO averages VALUES (9);
INSERT INTO averages VALUES (10);
-- calculate means
SELECT
  1/avg(1/val) AS harm,
  avg(val) AS arith
FROM
  averages;