I'm sure this will be a very simple question for most of you, but it is driving me crazy...
I have a table like this (simplifying):
| customer_id | date | purchase amount |
I need to extract, for each day, the number of customers that made a purchase that day, and the number of customers that made at least a purchase in the 30 days previous to the current one.
I tried using a subquery like this:
select purch_date as date, count (distinct customer_id) as DAU,
count(distinct (select customer_id from table where purch_date<= date and purch_date>date-30)) as MAU
from table
group by purch_date
Netezza returns an error saying that subqueries are not supported, and that I should think to rewrite the query. But how?!?!?
I tried using case when
statement, but did not work. In fact, the following:
select purch_date as date, count (distinct customer_id) as DAU,
count(distinct case when (purch_date<= date and purch_date>date-30) then player_id else null end) as MAU
from table
group by purch_date
returned no errors, but the MAU and DAU columns are the same (which is wrong).
Can anybody help me, please? thanks a lot
I don't beleive netezza supports subqueries in the select line...move to the from statement
select pur_date as date, count(distinct customer_id) as DAU
from table
group by purch_date
select pur_date as date, count (distinct customer_ID) as MAU
from table
where purch_date<= date and purch_date>date-30
group by purch_date
I hope thats right for MAU and DAU. join them to get the results combined:
select a.date, a.dau, b.mau
from
(select pur_date as date, count(distinct customer_id) as DAU
from table
group by purch_date) a
left join
(select pur_date as date, count (distinct customer_ID) as MAU
from table
where purch_date<= date and purch_date>date-30
group by purch_date) b
on b.date = a.date
I got it finally :) For all interested, here is the way I solved it:
select a.date_dt, max(a.dau), count(distinct b.player_id)
from (select dt.cal_day_dt as date_dt,
count(distinct s.player_id) as dau
FROM IA_PLAYER_SALES_HOURLY s
join IA_DATES dt on dt.date_key = s.date_key
group by dt.cal_day_dt
order by dt.cal_day_dt
) a
join (
select dt.cal_day_dt as date_dt,
s.player_id as player_id
FROM IA_PLAYER_SALES_HOURLY s
join IA_DATES dt on dt.date_key = s.date_key
order by dt.cal_day_dt
) b on b.date_dt <= a.date_dt and b.date_dt > a.date_dt - 30
group by a.date_dt
order by a.date_dt;
Hope this is helpful.