过滤行以仅获取最新值

Question

我在 table 中有以下数据：

ORDERID, PRODUCT,  QUANTITY
1,       potatoes, 10
1,       oranges,  20
2,       apples,   10
2,       oranges,  15
3,       pears,    20
3,       peaches,  12

我想查询 table 以过滤掉重复的产品（例如橙子），只取最新的（较高的 ORDERID）值。这应该导致：

ORDERID, PRODUCT,  QUANTITY
1,       potatoes, 10
2,       apples,   10
2,       oranges,  15
3,       pears,    20
3,       peaches,  12

Answer 1

select  *

from   (select      t.*
                   ,row_number () over (partition by PRODUCT order by ORDERID desc) as rn

        from        mytable t
        )

where   rn = 1

Answer 2

@Dudu 给出的答案的替代方法是子查询以查找每个产品的最大订单 ID，然后将其连接回您的原始 table 以限制您想要查看的记录.

SELECT t1.ORDERID,
       t1.PRODUCT,
       t1.QUANTITY
FROM yourTable t1
INNER JOIN
(
    SELECT PRODUCT, MAX(ORDERID) AS MAX_ORDERID
    FROM yourTable
    GROUP BY PRODUCT
) t2
    ON t1.PRODUCT = t2.PRODUCT AND
       t1.ORDERID = t2.MAX_ORDERID

过滤行以仅获取最新值

Filtering rows to get only the latest value

sql

oracle

greatest-n-per-group