CODEWITHSUNDEEP
sqlpostgresql
Stef
Stef

Reputation: 523

Get the newest entry before a GROUP BY query

Using postgres, I would like to retrieve each different packages, but retrieve the most recent package for each group.

For example, I have this table named products:

package_name        price           date
-               |   52500.0 |   20080910
-               |   52900.0 |   20090422
-               |   52900.0 |   20090706
ELITE PACKAGE   |   62200.0 |   20080910
ELITE PACKAGE   |   62500.0 |   20090706
ELITE PACKAGE   |   62500.0 |   20090422
TECH PACKAGE    |   57200.0 |   20080910
TECH PACKAGE    |   58200.0 |   20090706
TECH PACKAGE    |   58200.0 |   20090422

And I would like to get the following result with a SQL query:

-                   |   52900.0 |   20090706
ELITE PACKAGE       |   62500.0 |   20090706
TECH PACKAGE        |   58200.0 |   20090706

I have tried a couple of things that (I think) would have worked in mySQL, but I can't get it right for postgres.

Is it something possible to do, and how would I do it?

Thanks,

Stephanie

Upvotes: 3

Views: 408

Answers (2)

A Question Asker
A Question Asker

Reputation: 3311

Another option that avoids the self join (I always hate self joins)

SELECT package_name,price,date FROM
(
 SELECT package_name,price,date,
        ROW_NUMBER() OVER (PARTITION BY package_name ORDER BY date DESC) as rw
 FROM products
) a
WHERE rw=1;

Upvotes: 5

Joe Stefanelli
Joe Stefanelli

Reputation: 135808

SELECT t.package_name, p.price, t.MaxDate
    FROM (SELECT package_name, MAX(date) AS MaxDate
              FROM products
              GROUP BY package_name) t
        INNER JOIN products p
            ON t.package_name = p.package_name
                and t.MaxDate = p.date

Upvotes: 3

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