这将适用于几乎所有RDBM，

SELECT  a.*
FROM    tableName A
        INNER JOIN
        (
            SELECT partID, MAX(date) maxDate
            FROM    tableName
            GROUP BY partID
        ) B on a.partID = b.partID AND
                a.date = b.maxDate

• SQLFiddle演示

如果您的RDBMS支持Window Function，

SELECT  contractId ,date, price,partId
FROM    
(
    SELECT contractId ,date, price,partId,
            ROW_NUMBER() OVER (PARTITION BY PartID
                                ORDER BY date DESC) rn
    FROM    tableName
) s
WHERE   rn = 1

• SQLFiddle演示

SELECT c.*
FROM contracts c
    INNER JOIN 
    (
        SELECT partId, MAX([date]) AS MaxDate
        FROM contracts
        GROUP BY partID
    ) MaxDate
        ON c.partId = MaxDate.partID
            AND c.[date] = MaxDate.[date]

这是快速自联接：

SELECT c1.*  FROM contracts c1   
LEFT OUTER JOIN contracts c2 ON c2.partId = 1.partId AND c1.date < c2.date 
WHERE c2.contractId IS NULL

使用子选择（嵌套选择）往往较慢。