SQL Oracle Query self query - sql

Question

I am trying to figure out how to populate the below NULL values with 1.245 for dates from 07-OCT-14 to 29-SEP-14 then from 26-SEP-14 to 28-JUL-14 it will be 1.447.
This means if the date is less than or equal to the given date then use the value of max effective date which is less than the given date
We could select the last available index_ratio value for given security_alias and effective date <=p.effective_date , so in other words we will need to modify the sql to return from the subquery the index ratio value identified for the maximum available effective date assuming that this effective date is less or equal position effective date
How to populate the value ?
select ab.security_alias,
ab.index_ratio,
ab.effective_date
from securitydbo.security_analytics_fi ab
where ab.security_alias = 123627
order by ab.effective_date desc
Below should be the output

Answer 1

Assuming I understand your requirements correctly, I think the analytic function LAST_VALUE() is what you're after. E.g.:
with sample_data as (select 1 id, 10 val, to_date('01/08/2015', 'dd/mm/yyyy') dt from dual union all
select 1 id, null val, to_date('02/08/2015', 'dd/mm/yyyy') dt from dual union all
select 1 id, null val, to_date('03/08/2015', 'dd/mm/yyyy') dt from dual union all
select 1 id, null val, to_date('04/08/2015', 'dd/mm/yyyy') dt from dual union all
select 1 id, 20 val, to_date('05/08/2015', 'dd/mm/yyyy') dt from dual union all
select 1 id, 21 val, to_date('06/08/2015', 'dd/mm/yyyy') dt from dual union all
select 1 id, null val, to_date('07/08/2015', 'dd/mm/yyyy') dt from dual union all
select 1 id, null val, to_date('08/08/2015', 'dd/mm/yyyy') dt from dual union all
select 1 id, 31 val, to_date('09/08/2015', 'dd/mm/yyyy') dt from dual union all
select 1 id, null val, to_date('10/08/2015', 'dd/mm/yyyy') dt from dual union all
select 1 id, 42 val, to_date('11/08/2015', 'dd/mm/yyyy') dt from dual)
select id,
last_value(val ignore nulls) over (partition by id order by dt) val,
dt
from sample_data
order by id, dt desc;
ID VAL DT
---------- ---------- ----------
1 42 11/08/2015
1 31 10/08/2015
1 31 09/08/2015
1 21 08/08/2015
1 21 07/08/2015
1 21 06/08/2015
1 20 05/08/2015
1 10 04/08/2015
1 10 03/08/2015
1 10 02/08/2015
1 10 01/08/2015