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

query to find the top 3 in each type

Hi

I need help in finding the query which will provide the following resultset from the below table..

Table :
create table product_stocks(product_id int , product_type varchar(20) , no_of_units int)

Data:
insert into product_stocks values(1,'A',30)
insert into product_stocks values(2,'A',70)
insert into product_stocks values(3,'A',60)
insert into product_stocks values(4,'A',40)
insert into product_stocks values(1,'B',90)
insert into product_stocks values(2,'B',60)
insert into product_stocks values(3,'B',70)
insert into product_stocks values(4,'B',40)
insert into product_stocks values(1,'C',40)
insert into product_stocks values(2,'C',50)
insert into product_stocks values(3,'C',80)
insert into product_stocks values(4,'C',90)

Result Set:
product_type product_id no_of_units
----- ---- -----
A 2 70
A 3 60
A 4 40
B 1 90
B 3 70
B 2 60
C 4 90
C 3 80
C 2 50

i.e The result set gives the top 3 products in each product_type based on the no_of_units.

thanksselect * from product_stocks where product_id in (select top 3 product_id from product_stocks group by product_id )order by product_type,no_of_units desc|||harshal, fortunately for you, your solution has a wee flaw

by the way, did you not notice that this was another RFH post?

:)

RFH = request for homework|||Hi harshal,

Thanks for providing the query.
It was very helpful and met my requirement.

thanks|||harshal, fortunately for you, your solution has a wee flaw

by the way, did you not notice that this was another RFH post?

:)

RFH = request for homework

yeah I thought it would be a RFH..:mad: .

can u please enlighten me on the flaw part please...|||take a look at the subquery

you are grouping on product_id and then taking the top 3 of them

the top three based on what? there's no ORDER BY!!!!|||take a look at the subquery

you are grouping on product_id and then taking the top 3 of them

the top three based on what? there's no ORDER BY!!!!

OHH!! :confused:
I m getting lazy day by day.. need to spend more time on the forums i guess..;)

thanks for pointing out..

harshal|||Hi harshal

I tested the query , but the result is not correct .
It provides the result set for the product_id 1 , 2 , 3 in each product_type and not the
top 3 in each product_type based on no_of_units

thanks|||arjun, try this --select one.product_type
, one.product_id
, one.no_of_units
from daTable as one
inner
join daTable as two
on two.product_type = one.product_type
and two.no_of_units >= one.no_of_units
group
by one.product_type
, one.product_id
, one.no_of_units
having count(*) <= 3 and be sure you can explain it when your teacher asks you how you got it|||Hi

Even if order by is used in the sub query, it will give the top 3 product_id across all the product_type
But what i need is the top 3 from each of the product_type .

thanks|||Even if order by is used in the sub query, it will give the top 3 product_id across all the product_typeno, not if it's a correlated subquery

But what i need is the top 3 from each of the product_typedid you try my query?|||Hi r937 ,

I tried your query. It returns the top 3 product_id from all product_types.
I need another help.
In the result set , the order of the result set varies for each product_type.

product_type product_id no_of_units
----- ---- -----
A 2 70
A 3 60
A 4 40
B 1 90
B 2 60
B 3 70
C 2 50
C 3 80
C 4 90

How to modify this so that the no_of_units for each product_type is in the descending order.

thanks.|||I tried your query. It returns the top 3 product_id from all product_types.you could not possibly have tried it

here is what it produces:A 2 70
A 3 60
A 4 40
B 1 90
B 2 60
B 3 70
C 2 50
C 3 80
C 4 90this is exactly what you asked for|||Hi r937,

I am getting the same result as you have posted.

The Result set is here :

product_type product_id no_of_units
----- ---- -----
A 2 70
A 3 60
A 4 40
B 1 90
B 2 60
B 3 70
C 2 50
C 3 80
C 4 90

In this result set , the no_of_units for product_type 'A' is in descending order,
but the no_of_units for product_type 'B' and 'C' is not in descending order.

What i seek is to get the no_of_units in descending order for each of the product_types.

thanks|||look up ORDER BY in your manual

:)|||look up ORDER BY in your manual

:)
Firstly you must look up ORDER By in manual as r937 said ,thats for your knowledge..
well,this time just try this to get your results..

select one.product_type
, one.product_id
, one.no_of_units
from product_stocks as one
inner
join product_stocks as two
on two.product_type = one.product_type
and two.no_of_units >= one.no_of_units

group
by one.product_type
, one.product_id
, one.no_of_units

having count(*) <= 3 order by one.product_type,one.no_of_units desc

Joydeep|||This is coming pretty close to baby-sitting. arjun, you need to become familiar with books online. If you can't find your answer there, or you don't understand something, then post a question.