Left join Subquery but limit to first row - sql

Question

I am joining a metric table to a client listing. Currently when joined, the joined column populates for each client on all rows.
The goal is to only have the metric populate once per client grouping (hsp.PROV_ID). - SECOND IMAGE
select hsp.PROV_ID, HSP.id from hsp_client hsp
left join(select vat.ASGN_PROV_ID, sum(vat.ASGN_DFI_CNT) as 'Deficiency Count', sum(vat.DLQ_DFI_CNT) as 'Delinquent Count' from V_DT_PROV_ASGN_METRICS vat
where VAT.PAT_CLASS_C IN ('101', '102','104')
and VAT.METRIC_DATE = Convert(DATE, GetDate())
--and DEF_ID IS NULL
and vat.DEF_TYPE_C not in ('9')
group by vat.ASGN_PROV_ID,vat.ASGN_DFI_CNT,vat.DLQ_DFI_CNT
) vtt on vtt.ASGN_PROV_ID =hsp.PROV_ID
group by hsp.PROV_ID, hsp.id

Answer 1

If I understand your problem, you just want the metrics on the "first" row for each prov_id, where "first" row is defined by hsp.id.
You don't need aggregation in the outer query, just some logic on window functions:
select hsp.PROV_ID, HSP.id,
(case when hsp.id = min(hsp.id) over (partition by hsp.prov_id)
then vtt.DeficiencyCount
end) as DeficiencyCount,
(case when hsp.id = min(hsp.id) over (partition by hsp.prov_id)
then vtt.DelinquentCount
end),
from hsp_client hsp left join
(select vat.ASGN_PROV_ID, sum(vat.ASGN_DFI_CNT) as DeficiencyCount,
sum(vat.DLQ_DFI_CNT) as DelinquentCount
from V_DT_PROV_ASGN_METRICS vat
where VAT.PAT_CLASS_C IN ('101', '102','104') and
VAT.METRIC_DATE = Convert(DATE, GetDate()) and
--and DEF_ID IS NULL
vat.DEF_TYPE_C not in ('9')
group by vat.ASGN_PROV_ID
) vtt
on vtt.ASGN_PROV_ID = hsp.PROV_ID
order by hsp.PROV_ID, hsp.id;
This logic is more normally done in the application layer, but you can do it in SQL.
I'm not even sure the aggregation is needed in the subquery. But . . . it should be only at the "prov id" level.