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I have created a report with a query with parameters.

I have added the 'params' vector at property of query with the same name
of the parameter
ex:
sql="select .... where extract(year from fld1)=:var1
                   and extract(month from fld1)= :var2 ..."
params["var1"]=1990  
params["var2"]=2     

all the parameters are numbers (integer), but a message
" variable var1 not defined " occour and it not work.

In inspector the variables are present but not defined (null) and if i
set the value it's not saved, and the tool button in params generator is
not active. 

Where is the problem?

Andrea