Query with MAX Date

I have the following situation:
The name of a product can change with time. These changes are stored in a
table with 3 columns: Product_id, Date and ProductName with Product_id and
Date forming the Primary Key.
I want to run a query that returns the product_id and each product's latest
name. For the life of me, I can't get my head rould what such a query would
look like. I can get a query that gives me just the product_id and the Max
of Date with a group by on the Product_id but when I introduce the
ProductName, it returns ALL names.
I have a gut feeling that there may be a subquery involved, or am I barking
up the wrong tree?
Any help much appreciated.
PeteYou can either use a subquery:
SELECT Product_id, ProductName
FROM Your_table t1
WHERE Date = (SELECT MAX(Date) FROM Your_table t2 WHERE t1.Product_id =
t2.Product_id)
or a derived table:
SELECT t1.Product_id, t1.ProductName
FROM Your_table t1
INNER JOIN
(SELECT Product_id, MAX(Date) AS max_date
FROM Your_table
GROUP BY Product_id) t2
ON t1.Product_id = t2.Product_id
AND t1.Date = t2.max_date
Jacco Schalkwijk
SQL Server MVP
"Italian Pete" <ItalianPete@.discussions.microsoft.com> wrote in message
news:4847B525-302C-4354-99EE-8165C56B60D9@.microsoft.com...
>I have the following situation:
> The name of a product can change with time. These changes are stored in a
> table with 3 columns: Product_id, Date and ProductName with Product_id and
> Date forming the Primary Key.
> I want to run a query that returns the product_id and each product's
> latest
> name. For the life of me, I can't get my head rould what such a query
> would
> look like. I can get a query that gives me just the product_id and the
> Max
> of Date with a group by on the Product_id but when I introduce the
> ProductName, it returns ALL names.
> I have a gut feeling that there may be a subquery involved, or am I
> barking
> up the wrong tree?
> Any help much appreciated.
> Pete|||First, please change your column name 'Date' to something more meaningful
and something that doesn't use a reserved word. Also, you should be
consistent in your column naming. Why does Product_id have an underscore,
but ProductName not? Finally, in the future, please post DDL, sample data,
and desired results. See http://www.aspfaq.com/5006
In the meantime, you can try this:
SELECT o.Product_id, i.MaxDate, o.ProductName
FROM Products o
INNER JOIN
(
SELECT Product_id, MaxDate = MAX([Date])
FROM Products
GROUP BY Product_id
) i
ON o.Product_id = i.Product_id
AND o.[Date] = i.MaxDate
http://www.aspfaq.com/
(Reverse address to reply.)
"Italian Pete" <ItalianPete@.discussions.microsoft.com> wrote in message
news:4847B525-302C-4354-99EE-8165C56B60D9@.microsoft.com...
> I have the following situation:
> The name of a product can change with time. These changes are stored in a
> table with 3 columns: Product_id, Date and ProductName with Product_id and
> Date forming the Primary Key.
> I want to run a query that returns the product_id and each product's
latest
> name. For the life of me, I can't get my head rould what such a query
would
> look like. I can get a query that gives me just the product_id and the
Max
> of Date with a group by on the Product_id but when I introduce the
> ProductName, it returns ALL names.
> I have a gut feeling that there may be a subquery involved, or am I
barking
> up the wrong tree?
> Any help much appreciated.
> Pete|||Here is a solution based on guesswork:
SELECT t1.product_id, t1.product_name
FROM tbl t1
WHERE ( SELECT MAX( t2.dtcol )
FROM tbl t2
WHERE t2.product_id = t1.product_id ) = t1.dtcol ;
If this is not what you are looking for, refer to www.aspfaq.com/5006 and
provide required information.
Anith