Question

我有一个名为交易的表格，如下所示：

id      trade_date      trade_price     trade_status    seller_name
1       2015-01-02      150             open            Alex
2       2015-03-04      500             close           John
3       2015-04-02      850             close           Otabek
4       2015-05-02      150             close           Alex
5       2015-06-02      100             open            Otabek
6       2015-07-02      200             open            John

我想总结一下trade_price按seller_name分组的最后一次（trade_date）trade_status是否打开＆＃39;。那就是：

sum_trade_price     seller_name     
700                 John
950                 Otabek

跳过seller_name Alex 的行，因为上一个trade_status ＆＃39;关闭＆＃39; 。虽然我可以借助嵌套选择

获得理想的输出结果

SELECT SUM(t1.trade_price), t1.seller_name
WHERE t1.seller_name NOT IN 
                (SELECT t2.seller_name FROM trades t2 
                    WHERE t2.seller_name = t1.seller_name AND t2.trade_status = 'close' 
                    ORDER BY t2.trade_date DESC LIMIT 1)
from trades t1
group by t1.seller_name

但执行上述查询需要超过1分钟（我有大约100K行）。 还有另一种处理方法吗？ 我正在使用PostgreSQL。

Answer 1

我会用窗口函数来处理这个问题：

SELECT SUM(t.trade_price), t.seller_name
FROM (SELECT t.*,
             FIRST_VALUE(trade_status) OVER (PARTITION BY seller_name ORDER BY trade_date desc) as last_trade_status
      FROM trades t
     ) t
WHERE last_trade_status <> 'close;
GROUP BY t.seller_name;

Answer 2

这应该与seller_name

上的索引合理地执行

select
    sum(trade_price) as sum_trade_price,
    seller_name
from
    trades
    inner join
    (
        select distinct on (seller_name) seller_name, trade_status
        from trades
        order by seller_name, trade_date desc
    ) s using (seller_name)
where s.trade_status = 'open'
group by seller_name

SQL从表

2 个答案: