Simple Moving Average within a Script

[r3iuk]

I want to calculate a Simple Moving Average within my loading script. A SQL based example would be something like:

select a.quote_date, a.close_price, AVG(b.close_price) [20_day_sma] from
my_stock a
join my_stock b
on a.quote_date >= b.quote_date
and b.quote_date >= DATEADD(dd,-20,a.quote_date)
group by a.quote_date, a.close_price
order by 1

Is there a way to do this self join technique in QlikView?