rozenshtein method for pivoting relational data

I came across this blog entry while trying to make up for the fact that SQL server 8 does not have the PIVOT statement that I needed. It’s taken from a book (that I don’t have) by Rozenshtein on advanced database queries.
The blog explanation is lengthy and a little confusing but the idea is deceptively simple. It hinges around being able make a column expression that can ‘select’ data.

Continue reading “rozenshtein method for pivoting relational data”

secondary school mathematics that was almost useful

For the first time in my career I came across the need to make use of a PRODUCT() SQL aggregate function today. To my dismay SQL Server 8 doesn’t have such a function and so I figured out it can be simulated by use of logarithims and the SUM() function (since (log10(a) + log10(b))^10 = a * b) Therefore my query could read:

SELECT POWER(10, SUM(LOG10(value)))
FROM table

But this query doesn’t work if there are negative numbers in the PRODUCT() list because LOG10(x) where x<0 is undefined. Guess what, there’s a bunch of negative numbers in my list. Arghh … Continue reading “secondary school mathematics that was almost useful”