SQL query with IFs (?) to "Eliminate" NULL Values

[Stefan Schwarzer <stefan.schwarzer@xxxxxxxxxxxx>]

Hi there,

I want to calculate per Capita values on-the-fly, taking for example  
the "Total GDP" data set and divide it by "Total Population". Now,  
each of these data sets have a couple of "0" or "-9999" values (the  
latter being the indicator for : "no data available").

Until now I have it working like this:

    SELECT DISTINCT (tpes_total.y_2004 / pop_total.y_2004) AS  
y_2004, countries_view.name AS name
    FROM pop_total, countries_view
    LEFT JOIN tpes_total ON tpes_total.id = countries_view.id
    WHERE pop_total.y_2004<> '0' AND pop_total.y_2004<> '-9999' AND  
tpes_total.y_2004 <> '-9999' AND countries_view.id = pop_total.id
    ORDER BY name ASC

But then it eliminates the countries having these "0" or "-9999" values.

In principal I still would like to have them in my final $result, and  
then via PHP display them in grey (or with "x" or something like that).

So, I guess I'd need some kind of IF statement to do the calculation  
only with "valuable" numbers and pass the others as they are.

But I have no idea how this would work.

I would me most grateful if someone could give me a hint how to  
achieve that.

Thanks a lot.

Stef

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