Loop in Oracle SQL, comparing one month to another - sql

Question

I have to draft a SQL query which does the following:
Compare current week (e.g. week 10) amount to the average amount over previous 4 weeks (Week# 9,8,7,6).
Now I need to run the query on a monthly basis so say for weeks (10,11,12,13).
As of now I am running it four times giving the week parameter on each run.
For example my current query is something like this :
select account_id, curr.amount,hist.AVG_Amt
from
(
select
to_char(run_date,'IW') Week_ID,
sum(amount) Amount,
account_id
from Transaction t
where to_char(run_date,'IW') = '10'
group by account_id,to_char(run_date,'IW')
) curr,
(
select account_id,
sum(amount) / count(to_char(run_date,'IW')) as AVG_Amt
from Transactions
where to_char(run_date,'IW') in ('6','7','8','9')
group by account_id
) hist
where
hist.account_id = curr.account_id
and curr.amount > 2*hist.AVG_Amt;
As you can see, if I have to run the above query for week 11,12,13 I have to run it three separate times. Is there a way to consolidate or structure the query such that I only run once and I get the comparison data all together?
Just an additional info, I need to export the data to Excel (which I do after running query on the PL/SQL developer) and export to Excel.
Thanks!
-Abhi

Answer 1

You can use a correlated sub-query to get the sum of amounts for the last 4 weeks for a given week.
select
to_char(run_date,'IW') Week_ID,
sum(amount) curAmount,
(select sum(amount)/4.0 from transaction
where account_id = t.account_id
and to_char(run_date,'IW') between to_char(t.run_date,'IW')-4
and to_char(t.run_date,'IW')-1
) hist_amount,
account_id
from Transaction t
where to_char(run_date,'IW') in ('10','11','12','13')
group by account_id,to_char(run_date,'IW')
Edit: Based on OP's comment on the performance of the query above, this can also be accomplished using lag to get the previous row's value. Count of number of records present in the last 4 weeks can be achieved using a case expression.
with sum_amounts as
(select to_char(run_date,'IW') wk, sum(amount) amount, account_id
from Transaction
group by account_id, to_char(run_date,'IW')
)
select wk, account_id, amount,
1.0 * (lag(amount,1,0) over (order by wk) + lag(amount,2,0) over (order by wk) +
lag(amount,3,0) over (order by wk) + lag(amount,4,0) over (order by wk))
/ case when lag(amount,1,0) over (order by wk) <> 0 then 1 else 0 end +
case when lag(amount,2,0) over (order by wk) <> 0 then 1 else 0 end +
case when lag(amount,3,0) over (order by wk) <> 0 then 1 else 0 end +
case when lag(amount,4,0) over (order by wk) <> 0 then 1 else 0 end
as hist_avg_amount
from sum_amounts

Answer 2

I think that is what you are looking for:
with lagt as (select to_char(run_date,'IW') Week_ID, sum(amount) Amount, account_id
from Transaction t
group by account_id, to_char(run_date,'IW'))
select Week_ID, account_id, amount,
(lag(amount,1,0) over (order by week) + lag(amount,2,0) over (order by week) +
lag(amount,3,0) over (order by week) + lag(amount,4,0) over (order by week)) / 4 as average
from lagt;