[ZOPE] Pb with ZGDchart or ZSQLMethod ??

Hello, I have a problem with ZGDChart 0.6.2 . I've linked it to a ZSQLMethod (via an ZODBC Database Connection) to plot data curves. When, at least, 1 data misses, there's no graph plotted. How can I do to plot this even if I got misses ? (NB: I've tried the SQL fonction nvl(col,substitute value) into my SQL Method to obtain values when ODBC returns no values, but it doesn't work !!) Thanks. mailto david.peyrieres@meteo.fr