How do I find the oldest date in Group - sql

Question

I have a table where I need to get the oldest date from a group and be able to return all rows. I'm finding it difficult since I need to return the system_id field.
AssignedProfsHistory MatterID EffectiveDate
1 33434-3344 08/22/2005
2 33434-3344 07/12/2004
3 33434-3344 07/12/2004
4 21122-323 12/05/2007
5 43332-986 10/18/2014
6 43332-986 03/23/2013
So in this example, the rows for systemid 2 & 3 should return because they are tied for earliest date. The row for systemid 4 should return and systemid 6 should be returned.
This is what I have so far. Because I need to include the systemid(AssignedProfHistory) I'm not getting the results I need.
SELECT aph.AssignedProfsHistory,
m.MatterID,
Min(aph.EffectiveDate) as 'EffectiveDate'
from AssignedProfsHistory aph
INNER JOIN Matters m
ON aph.Matters = m.Matters
WHERE aph.AssignedType = 'Originating'
Group by m.matters,m.matterid,aph.assignedprofshistory
order by m.MatterID
Any idea how to get the results I need?
Thank you in advance.

Answer 1

select AssignedProfsHistory, MatterID, EffectiveDate
from (
SELECT
aph.AssignedProfsHistory,
m.MatterID,
aph.EffectiveDate,
row_number() over(partition by m.MatterID order by aph.EffectiveDate) as rn
from AssignedProfsHistory aph
INNER JOIN Matters m ON aph.Matters = m.Matters
WHERE aph.AssignedType = 'Originating'
) t
where rn = 1;
You can use the row_number window function to assign row numbers to dates for each matterid. Because the ordering is based on the ascending EffectiveDate, rows with the oldest date get assigned 1 and you select those.
If a matterid can have multiple rows with the oldest dates, you can use rank or dense_rank to get all the rows for the oldest date.

Answer 2

Since you want to keep the ties, I'd do it like this:
SELECT t2.AssignedProfsHistory, m.MatterID, t2.EffectiveDate
FROM (
SELECT MatterID, MIN(EffectiveDate) med
FROM AssignedProfsHistory
WHERE AssignedType = 'Originating'
GROUP BY MatterID
) t1
INNER JOIN AssignedProfsHistory t2 ON t2.MatterID = t1.MatterID
and t2.EffectiveDate = t1.med and t2.AssignedType = 'Originating'
INNER JOIN Matters m on m.Matters = t2.Matters
ORDER BY m.MatterId
Here is an SQLFiddle without the Matters table that demonstrates it can work, no windowing functions or CTE required, though a CTE would allow you to avoid repeating the AssignedType='Originating' condition.

Answer 3

this should get you what you need
with cte as (
SELECT aph.AssignedProfsHistory,
m.MatterID,
aph.EffectiveDate as 'EffectiveDate'
from AssignedProfsHistory aph
INNER JOIN Matters m
ON aph.Matters = m.Matters
WHERE aph.AssignedType = 'Originating'
Group by m.matters,m.matterid,aph.assignedprofshistory
)
select
AssignedProfsHistory,
MatterID,
EffectiveDate
from
cte
join (
select
min(EffectiveDate) min_effectivedate,
MatterID
from
cte
group by
MatterID
) b on cte.EffectiveDate = b.min_effectivedate and
cte.MatterID = b.MatterID
order by AssignedProfsHistory

Answer 4

First take the older date and then join it with your table.
WITH OlderAPH AS (
SELECT
AssignedProfsHistory,
Matters,
MIN(EffectiveDate) OlderDate
FROM AssignedProfsHistory
WHERE AssignedType = 'Originating'
GROUP BY Matters, AssignedProfsHistory )
SELECT
O.AssignedProfsHistory, M.MatterID, O.OlderDate
FROM OlderAPH O
INNER JOIN Matters M ON O.Matters = M.Matters
ORDER BY M.MatterID