"Marty Meyers" <martym@execpc.com> wrote in message
news:1221g89ld0dtoab@corp.supernews.com...
> if (ColA=0)
> { // use Col B}
>
> elseif(ColA > 0 && colA < ColB)
> { // use Col A
> }
> else
> { //use ColB}

SELECT ...
ORDER BY CASE
WHEN ColA = 0 THEN ColB
WHEN ColA > 0 AND ColA < ColB THEN ColA
ELSE ColB
END

It's based on the fact that the arguments to ORDER BY are expressions, not
simply column names. You can use things like CASE and IF() to make
interesting, complex expressions. Read more about these functions here:
http://dev.mysql.com/doc/refman/5.0/...functions.html

> The MsSQL manual doesn't seem to cover this, nor does the two beginner
> books I have. A pointer to a reference where I can learn about advanced
> "Order by" would be great

It's not much, but here's an article I found through Google:
http://www.sqlteam.com/item.asp?ItemID=2209
It's written for Microsoft SQL Server users, but it mostly applies to MySQL
as well.

Regards,
Bill K.