T-SQL Subquery Max(Date) and Joins - sql

Question

I'm trying to join multiple tables, but one of the tables has multiple records for a partid with different dates. I want to get the record with the most recent date.
Here are some example tables:
Table: MyParts
Partid Partnumber Description
1 ABC-123 Pipe
2 ABC-124 Handle
3 ABC-125 Light
Table: MyPrices
Partid Price PriceDate
1 $1 1/1/2005
1 $2 1/1/2007
1 $3 1/1/2009
2 $2 1/1/2005
2 $4 1/1/2006
2 $5 1/1/2008
3 $10 1/1/2008
3 $12 1/1/2009
If I was just wanted to find the most recent price for a certain part I could do:
SELECT * FROM MyPrice WHERE PriceDate = (SELECT MAX(PriceDate)
FROM MyPrice WHERE Partid = 1)
However I want to do a join first and get back the correct price for all parts not just one. This is what I have tried:
SELECT * FROM MyParts LEFT JOIN MyPrice ON MyParts.Partid = MyPrice.Partid WHERE
MyPart.PriceDate = (SELECT MAX(PriceDate) FROM MyPrice)
The results are wrong as it takes the highest price date of the entire table.
SELECT * FROM MyParts LEFT JOIN MyPrice ON MyParts.Partid = MyPrice.Partid WHERE
MyPart.PriceDate = (SELECT MAX(PriceDate) FROM MyPrice WHERE MyPrice.Partid =
MyParts.Partid)
That errors out.
What can I do to get the results I want.

Answer 1

Here's another way to do it without subqueries. This method will often outperform others, so it's worth testing both methods to see which gives the best performance.
SELECT
PRT.PartID,
PRT.PartNumber,
PRT.Description,
PRC1.Price,
PRC1.PriceDate
FROM
MyParts PRT
LEFT OUTER JOIN MyPrices PRC1 ON
PRC1.PartID = PRT.PartID
LEFT OUTER JOIN MyPrices PRC2 ON
PRC2.PartID = PRC1.PartID AND
PRC2.PriceDate > PRC1.PriceDate
WHERE
PRC2.PartID IS NULL
This will give multiple results if you have two prices with the same EXACT PriceDate (Most other solutions will do the same). Also, I there is nothing to account for the last price date being in the future. You may want to consider a check for that regardless of which method you end up using.

Answer 2

Try this:
Select *,
Price = (Select top 1 Price
From MyPrices
where PartID = mp.PartID
order by PriceDate desc
)
from MyParts mp

Answer 3

SELECT
MyParts.*,MyPriceDate.Price,MyPriceDate.PriceDate
FROM MyParts
INNER JOIN (SELECT Partid, MAX(PriceDate) AS MaxPriceDate FROM MyPrice GROUP BY Partid) dt ON MyParts.Partid = dt.Partid
INNER JOIN MyPrice ON dt.Partid = MyPrice.Partid AND MyPrice.PriceDate=dt.MaxPriceDate

Answer 4

In SQL Server 2005 and later use ROW_NUMBER():
SELECT * FROM
( SELECT p.*,
ROW_NUMBER() OVER(PARTITION BY Partid ORDER BY PriceDate DESC) AS rn
FROM MyPrice AS p ) AS t
WHERE rn=1

Answer 5

Something like this
SELECT *
FROM MyParts
LEFT JOIN
(
SELECT MAX(PriceDate), PartID FROM MyPrice group by PartID
) myprice
ON MyParts.Partid = MyPrice.Partid
If you know your partid or can restrict it put it inside the join.
SELECT myprice.partid, myprice.partdate, myprice2.Price, *
FROM MyParts
LEFT JOIN
(
SELECT MAX(PriceDate), PartID FROM MyPrice group by PartID
) myprice
ON MyParts.Partid = MyPrice.Partid
Inner Join MyPrice myprice2
on myprice2.pricedate = myprice.pricedate
and myprice2.partid = myprice.partid

Answer 6

SELECT
*
FROM
(SELECT MAX(PriceDate) AS MaxP, Partid FROM MyPrices GROUP BY Partid) MaxP
JOIN
MyPrices MP On MaxP.Partid = MP.Partid AND MaxP.MaxP = MP.PriceDate
JOIN
MyParts P ON MP.Partid = P.Partid
You to get the latest pricedate for partid first (a standard aggregate), then join it back to get the prices (which can't be in the aggregate), followed by getting the part details.

Answer 7

Join on the prices table, and then select the entry for the last day:
select pa.partid, pa.Partnumber, max(pr.price)
from myparts pa
inner join myprices pr on pr.partid = pa.partid
where pr.PriceDate = (
select max(PriceDate)
from myprices
where partid = pa.partid
)
The max() is in case there are multiple prices per day; I'm assuming you'd like to display the highest one. If your price table has an id column, you can avoid the max() and simplify like:
select pa.partid, pa.Partnumber, pr.price
from myparts pa
inner join myprices pr on pr.partid = pa.partid
where pr.priceid = (
select max(priceid)
from myprices
where partid = pa.partid
)
P.S. Use wcm's solution instead!

Answer 8

All other answers must work, but using your same syntax (and understanding why the error)
SELECT * FROM MyParts LEFT JOIN MyPrice ON MyParts.Partid = MyPrice.Partid WHERE
MyPart.PriceDate = (SELECT MAX(MyPrice2.PriceDate) FROM MyPrice as MyPrice2
WHERE MyPrice2.Partid = MyParts.Partid)

Answer 9

Please try next code example:
select t1.*, t2.partprice, t2.partdate
from myparts t1
join myprices t2
on t1.partid = t2.partid
where partdate =
(select max(partdate) from myprices t3
where t3.partid = t2.partid group by partid)

Answer 10

For MySQL, please find the below query:
select * from (select PartID, max(Pricedate) max_pricedate from MyPrices group bu partid) as a
inner join MyParts b on
(a.partid = b.partid and a.max_pricedate = b.pricedate)
Inside the subquery it fetches max pricedate for every partyid of MyPrices then,
inner joining with MyParts using partid and the max_pricedate