How Can I Calculate the Product of Values in Oracle SQL?

Calculating Product of Values in Oracle SQL

A colleague poses the question: can Oracle SQL evaluate a function akin to the SUM function but for multiplying values? To our knowledge, Oracle SQL does not offer such an explicit product function. However, there is a practical technique to simulate this operation using logarithmic and exponential calculations.

Consider the following query:

SELECT PRODUCT(X)
FROM
(
    SELECT 3 X FROM DUAL
    UNION ALL 
    SELECT 5 X FROM DUAL
    UNION ALL
    SELECT 2 X FROM DUAL
)

With this, we seek to obtain the product of the X values, which would be 30 (3 x 5 x 2). Here's the workhorse formula:

select exp(sum(ln(col)))
  from table;

In this formula:

• exp() calculates the natural exponential of the sum of the natural logarithm of each value in the specified column ('col').
• ln() calculates the natural logarithm of each value in 'col.'
• sum() adds up the results of the logarithmic calculations.

For instance, with the given values (3, 5, 2), the formula unfolds as follows:

exp(ln(3) + ln(5) + ln(2))
= exp(1.0986122886681096 + 1.6094379124341003 + 0.6931471805599453)
= exp(3.3912025714812163)
= 29.999999701269282

When 'col' contains only positive values, this technique provides accurate results. For non-positive values, alternative approaches may be necessary.

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