CODEWITHSUNDEEP
sqlsql-servert-sqljoinsubquery
MaxGeek
MaxGeek

Reputation: 1105

T-SQL Subquery Max(Date) and Joins

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.

Upvotes: 28

Views: 111137

Answers (10)

A-K
A-K

Reputation: 17070

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

Upvotes: 7

KM.
KM.

Reputation: 103579

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

Upvotes: 11

Suren
Suren

Reputation: 35

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

Upvotes: 0

Rupal
Rupal

Reputation: 59

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)

Upvotes: 0

Tom H
Tom H

Reputation: 47444

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.

Upvotes: 36

wcm
wcm

Reputation: 9281

Try this:

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

Upvotes: 35

u07ch
u07ch

Reputation: 13692

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

Upvotes: 5

Andomar
Andomar

Reputation: 238048

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!

Upvotes: 3

Eduardo Molteni
Eduardo Molteni

Reputation: 39413

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)

Upvotes: 2

gbn
gbn

Reputation: 432180

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.

Upvotes: 3

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