how to get sum of amount for previous 3 months (dynamically)

[compbiz]

I have 3 tables
district
dist_code dist_name
11 LA
12 WA

demands
dist_name year demandfortheyear
LA 1999 3434.44

dues
dist_name month year currentdue
LA 1 1999 890
LA 2 1999 656
LA 3 1999 455
LA 4 1999 4554

if current year is 1999 and month is 4 I want to retrieve it from system date and get sum of currentdue for previous 3 months(1 to 3)

 

[Poseidon]

hi

try ist this way:

select sum(currentdue)
from dues
where year = year(current date)
and month < month(current date)


martin