Sql

/* Convert the annualized number back to a percent */
SELECT (T3.AnnHPR - 1) * 100 AS GeomAnnRet
FROM
  (
  /* Annualize the holding period return */
  SELECT POWER(T2.HPR, 12.0 / T2.NumReturns) AS AnnHPR
  FROM
    (
    /* Calculate the holding period return over the time
       period.

       POWER(10, SUM(LOG10(n))) is a simulated PRODUCT(n)
       aggregate function.

       The precision of POWER is determined by the precision
        of the first argument, so use a lot of decimals. */
    SELECT POWER(10.0000000000000000,
                 SUM(LOG10(T.MonthReturn))) AS HPR,
           COUNT(*) AS NumReturns
    FROM
      (
      /* Convert all percent returns to multipliers (1% ->
         1.01) */
      SELECT 1 + MonthPctReturn / 100 AS MonthReturn
      FROM ...
      ) AS T
    ) AS T2
  ) AS T3