Question

I have table like this:

type       | date       | id
-----------------------------
1          | 2012-01-01 | 1
2          | 2012-01-01 | 2
1          | 2012-02-02 | 3
2          | 2012-02-02 | 4

I need to build query that will pick all “up-to-date” distinct values of type ( in this example it will be records with id’s 3 and 4). Now i have this solution :

select * from test t1 where date = 
(select max(date) from test t2 where t2.type = t1.type ) order by type, date desc

I am embarrassed by the presence of nested select, maybe there is more elegant solution ?

Answer 1

since you didn’t mention the RDBMS you are using, try this one. will work on most RDBMS.

SELECT  a.*
FROM    tableName a
        INNER JOIN
        (
            SELECT  type, MAX(DATE) maxDAte
            FROM tableName
            GROUP BY type
        ) b ON a.type = b.type AND
                a.DATE = b.maxDate

• SQLFiddle Demo

or if you RDBMS supports Window Function

SELECT type, date, id
FROM
(
    SELECT type, date, id,
            ROW_NUMBER() OVER (PARTITION BY type
                                ORDER BY date DESC) rn
    FROM tableNAme
) s
WHERE rn = 1

• SQLFiddle Demo