The expression for the product of a column from logarithm and exponential functions is:

SELECT ((EXP (SUM (LN (CASE WHEN nbr = 0.00
                            THEN NULL
                            ELSE ABS(nbr) END))))
  * (CASE WHEN MIN (ABS (nbr)) = 0.00
          THEN 0.00
          ELSE 1.00 END)
  * (CASE WHEN MOD (SUM (CASE WHEN SIGN(nbr) = -1
                               THEN 1
                               ELSE 0 END), 2) = 1
           THEN -1.00
           ELSE 1.00 END) AS big_pi
 FROM NumberTable;

The nice part of this is that you can also use the SUM (DISTINCT <expression>) option to get the equivalent of PRD (DISTINCT <expression>).

You should watch the data type of the column involved and use either integer 0 and 1 or decimal 0.00 and 1.00 as is appropriate in the CASE statements.  It is worth studying the three CASE expressions that make up the terms of the Prod calculation.

The first CASE expression is to insure that all zeros and negative numbers are converted to a non-negative or NULL for the SUM() function, just in case your SQL raises an exception.

The second CASE expression will return zero as the answer if there was a zero in the nbr column of any selected row.  The MIN(ABS(nbr)) is a handy trick for detecting the existence of a zero in a list of both positive and negative numbers with an aggregate function.

The third CASE expression will return minus one if there was an odd number of negative numbers in the nbr column.  The innermost CASE expression uses a SIGN() function which returns +1 for a positive number, -1 for a negative number and 0 for a zero.  The SUM() counts the -1 results then the MOD() functions determines if the count was odd or even.