Hot to get a average value on analytic function - sql

Question

I have to get the average value on this BAL column for each account
with cte as (
select distinct t.DATE_ID,
ad.ACCOUNT_ID
from TIMEDATE t
, ACCOUNT_DLY ad)
select cte.date_id,
cte.Account_ID,
NVL(current_bal,lag (ad.current_bal) ignore nulls over (PARTITION by cte.account_id order by cte.date_id )) as bal
from cte left join ACCOUNT_DLY ad
on cte.date_id = ad.SRC_EXTRACT_DT
and cte.ACCOUNT_ID = ad.ACCOUNT_ID
order by 2,1;
I guess I need to use analytic function SUM or AVG again with partition on the NVL
on the top of the picture is my table on the bottom is how it suppose to look like
https://i.stack.imgur.com/H2Dql.png

Answer 1

Analytic vs Aggregate Function
You probably should use aggregate function AVG() ... GROUP BY instead of analytic function AVG() OVER(). The difference is that aggregate function returns one and only one row per columns it is grouped by. Analytic function puts the result in every resulting row and, in the sample as yours, that means use of DISTINCT keyword to eliminate duplicate rows which could be performance costly with bigger datasets. You can have the same result using aggregate or analytic function, though.
This is just to compare one and another - if your data is like this:
WITH
tbl AS
(
Select 1 "ID", To_Date('01-JAN-2023', 'dd-MON-yyyy') "A_DATE", 6 "A_VALUE" From Dual Union All
Select 1 "ID", To_Date('02-JAN-2023', 'dd-MON-yyyy') "A_DATE", 7 "A_VALUE" From Dual Union All
Select 1 "ID", To_Date('03-JAN-2023', 'dd-MON-yyyy') "A_DATE", 8 "A_VALUE" From Dual Union All
Select 2 "ID", To_Date('01-JAN-2023', 'dd-MON-yyyy') "A_DATE", 9 "A_VALUE" From Dual Union All
Select 2 "ID", To_Date('02-JAN-2023', 'dd-MON-yyyy') "A_DATE", 9 "A_VALUE" From Dual Union All
Select 2 "ID", To_Date('03-JAN-2023', 'dd-MON-yyyy') "A_DATE", 9 "A_VALUE" From Dual Union All
Select 3 "ID", To_Date('01-JAN-2023', 'dd-MON-yyyy') "A_DATE", 6 "A_VALUE" From Dual Union All
Select 3 "ID", To_Date('02-JAN-2023', 'dd-MON-yyyy') "A_DATE", 3 "A_VALUE" From Dual Union All
Select 3 "ID", To_Date('03-JAN-2023', 'dd-MON-yyyy') "A_DATE", 6 "A_VALUE" From Dual Union All
--
Select 1 "ID", To_Date('01-FEB-2023', 'dd-MON-yyyy') "A_DATE", 4 "A_VALUE" From Dual Union All
Select 1 "ID", To_Date('02-FEB-2023', 'dd-MON-yyyy') "A_DATE", 3 "A_VALUE" From Dual Union All
Select 1 "ID", To_Date('03-FEB-2023', 'dd-MON-yyyy') "A_DATE", 2 "A_VALUE" From Dual Union All
Select 2 "ID", To_Date('01-FEB-2023', 'dd-MON-yyyy') "A_DATE", 6 "A_VALUE" From Dual Union All
Select 2 "ID", To_Date('02-FEB-2023', 'dd-MON-yyyy') "A_DATE", 6 "A_VALUE" From Dual Union All
Select 2 "ID", To_Date('03-FEB-2023', 'dd-MON-yyyy') "A_DATE", 6 "A_VALUE" From Dual Union All
Select 3 "ID", To_Date('01-FEB-2023', 'dd-MON-yyyy') "A_DATE", 6 "A_VALUE" From Dual Union All
Select 3 "ID", To_Date('02-FEB-2023', 'dd-MON-yyyy') "A_DATE", 9 "A_VALUE" From Dual Union All
Select 3 "ID", To_Date('03-FEB-2023', 'dd-MON-yyyy') "A_DATE", 6 "A_VALUE" From Dual
)
... then use of aggregate function gives you the result you wanted...
-- Aggregate Function AVG() ... GROUP BY
Select DISTINCT
ID, To_Char(A_DATE, 'yyyymm') "MTH", AVG(A_VALUE) "AVG_VALUE"
From
tbl
Group By
ID, To_Char(A_DATE, 'yyyymm')
Order By
To_Char(A_DATE, 'yyyymm'), ID
/*
ID MTH AVG_VALUE
---------- ------ ----------
1 202301 7
2 202301 9
3 202301 5
1 202302 3
2 202302 6
3 202302 7
*/
... on the other hand, using analytic function (without DISTINCT keyword) will result with the same AVG value in all rows with same ID and MONTH...
-- Analytic Function AVG() OVER()
Select --DISTINCT
ID, To_Char(A_DATE, 'yyyymm') "MTH", AVG(A_VALUE) OVER(Partition By ID, To_Char(A_DATE, 'yyyymm') ) "AVG_VALUE"
From
tbl
Order By
To_Char(A_DATE, 'yyyymm'), ID
/*
ID MTH AVG_VALUE
---------- ------ ----------
1 202301 7
1 202301 7
1 202301 7
2 202301 9
2 202301 9
2 202301 9
3 202301 5
3 202301 5
3 202301 5
1 202302 3
1 202302 3
1 202302 3
2 202302 6
2 202302 6
2 202302 6
3 202302 7
3 202302 7
3 202302 7
... and if you put the DISTINCT keyword in your Select statement you will get the same result as with aggregate function above
-- using DISTINCT
/*
ID MTH AVG_VALUE
---------- ------ ----------
1 202301 7
2 202301 9
3 202301 5
1 202302 3
2 202302 6
3 202302 7
*/