Sql 选择不同的地方

Question

我正在尝试求和 select:

select sum(price) as 'total', currency_id
from reports
group by currency_id

但是 table 包含一个名为 transaction_id 的行，一旦计算总和我想只计算具有不同 transaction_id 值的行，我如何创建它在哪里？

Answer 1

如果你想对每个交易id统计一次，那么你可以使用window函数：

select sum(price) as total, currency_id
from (select r.*,
             row_number() over (partition by transaction_id order by transaction_id) as seqnum
      from reports r
     ) r
where seqnum = 1
group by currency_id;

如果你想对只出现一次的 transaction_id 求和，你仍然可以使用 window 函数，但有一个区别：

select sum(price) as total, currency_id
from (select r.*,
             count(*) over (partition by transaction_id) as cnt
      from reports r
     ) r
where cnt = 1
group by currency_id;

Sql 选择不同的地方

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