Use of MAX function in SQL query to filter data - sql

Question

The code below joins two tables and I need to extract only the latest date per account, though it holds multiple accounts and history records. I wanted to use the MAX function, but not sure how to incorporate it for this case. I am using My SQL server.
Appreciate any help !
select
PROP.FileName,PROP.InsName, PROP.Status,
PROP.FileTime, PROP.SubmissionNo, PROP.PolNo,
PROP.EffDate,PROP.ExpDate, PROP.Region,
PROP.Underwriter, PROP_DATA.Data , PROP_DATA.Label
from
Property.dbo.PROP
inner join
Property.dbo.PROP_DATA on Property.dbo.PROP.FileID = Actuarial.dbo.PROP_DATA.FileID
where
(PROP_DATA.Label in ('Occupancy' , 'OccupancyTIV'))
and (PROP.EffDate >= '42278' and PROP.EffDate <= '42643')
and (PROP.Status = 'Bound')
and (Prop.FileTime = Max(Prop.FileTime))
order by
PROP.EffDate DESC

Answer 1

Assuming your DBMS supports windowing functions and the with clause, a max windowing function would work:
with all_data as (
select
PROP.FileName,PROP.InsName, PROP.Status,
PROP.FileTime, PROP.SubmissionNo, PROP.PolNo,
PROP.EffDate,PROP.ExpDate, PROP.Region,
PROP.Underwriter, PROP_DATA.Data , PROP_DATA.Label,
max (PROP.EffDate) over (partition by PROP.PolNo) as max_date
from Actuarial.dbo.PROP
inner join Actuarial.dbo.PROP_DATA
on Actuarial.dbo.PROP.FileID = Actuarial.dbo.PROP_DATA.FileID
where (PROP_DATA.Label in ('Occupancy' , 'OccupancyTIV'))
and (PROP.EffDate >= '42278' and PROP.EffDate <= '42643')
and (PROP.Status = 'Bound')
and (Prop.FileTime = Max(Prop.FileTime))
)
select
FileName, InsName, Status, FileTime, SubmissionNo,
PolNo, EffDate, ExpDate, Region, UnderWriter, Data, Label
from all_data
where EffDate = max_date
ORDER BY EffDate DESC
This also presupposes than any given account would not have two records on the same EffDate. If that's the case, and there is no other objective means to determine the latest account, you could also use row_numer to pick a somewhat arbitrary record in the case of a tie.

Answer 2

Using straight SQL, you can use a self-join in a subquery in your where clause to eliminate values smaller than the max, or smaller than the top n largest, and so on. Just set the number in <= 1 to the number of top values you want per group.
Something like the following might do the trick, for example:
select
p.FileName
, p.InsName
, p.Status
, p.FileTime
, p.SubmissionNo
, p.PolNo
, p.EffDate
, p.ExpDate
, p.Region
, p.Underwriter
, pd.Data
, pd.Label
from Actuarial.dbo.PROP p
inner join Actuarial.dbo.PROP_DATA pd
on p.FileID = pd.FileID
where (
select count(*)
from Actuarial.dbo.PROP p2
where p2.FileID = p.FileID
and p2.EffDate <= p.EffDate
) <= 1
and (
pd.Label in ('Occupancy' , 'OccupancyTIV')
and p.Status = 'Bound'
)
ORDER BY p.EffDate DESC
Have a look at this stackoverflow question for a full working example.

Answer 3

Not tested
with temp1 as
(
select foo
from bar
whre xy = MAX(xy)
)
select PROP.FileName,PROP.InsName, PROP.Status,
PROP.FileTime, PROP.SubmissionNo, PROP.PolNo,
PROP.EffDate,PROP.ExpDate, PROP.Region,
PROP.Underwriter, PROP_DATA.Data , PROP_DATA.Label
from Actuarial.dbo.PROP
inner join temp1 t
on Actuarial.dbo.PROP.FileID = t.dbo.PROP_DATA.FileID
ORDER BY PROP.EffDate DESC