获取序列中的最后一个值

Question

我正在尝试 return 特定事件序列中的最后一个值，我最初的想法是使用 LAST_VALUE() 但我无法让它工作。我可以用子查询和连接来做到这一点，但是是否有一个 window 函数可以更容易地给出这个结果？

现在查询正在提取最大数量，但我想要的是基于 seq 列的 last 数量

数据

| PaymentID |          Description | Result | Seq |
|-----------|----------------------|--------|-----|
|         1 | Entered Payment Page |    Yes |   1 |
|         1 |       Amount Entered |     50 |   2 |
|         1 |       Amount Entered |     60 |   3 |
|         1 |       Amount Entered |     20 |   4 |
|         1 |     Amount Confirmed |    Yes |   5 |
|         2 | Entered Payment Page |    Yes |   1 |
|         2 |       Amount Entered |    100 |   2 |
|         2 |     Amount Confirmed |    Yes |   3 |
|         3 | Entered Payment Page |    Yes |   1 |
|         3 |       Amount Entered |      4 |   2 |
|         3 |     Amount Confirmed |     No |   3 |
|         3 |       Amount Entered |      8 |   4 |
|         3 |     Amount Confirmed |    Yes |   5 |

当前查询结果

| PaymentID | InPayment | Amount | Confirmed |
|-----------|-----------|--------|-----------|
|         1 |       Yes |     60 |       Yes |
|         2 |       Yes |    100 |       Yes |
|         3 |       Yes |      8 |       Yes |

想要的结果

| PaymentID | InPayment | Amount | Confirmed |
|-----------|-----------|--------|-----------|
|         1 |       Yes |     20 |       Yes |
|         2 |       Yes |    100 |       Yes |
|         3 |       Yes |      8 |       Yes |

Answer 1

您可以使用 row_number() 和条件聚合：

select paymentid,
       max(case when description = 'Entered Payment Page' then result end) as inpayment,
       max(case when description = 'Amount Entered' then result end) as amount_entered,
       max(case when description = 'Amount Confirmed' then result end) as amount_confirmed
from (select t.*,
             row_number() over (partition by paymentid, description order by seq desc) as seqnum
      from paymentinfo t
     ) t
where seqnum = 1
group by paymentid;

Here 是 SQL Fiddle.

获取序列中的最后一个值

Get last value in sequence

sql

tsql

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