字符串聚合

Question

我的源表如下所示：

Account_Number, Code, Transaction_Amount, Comment, Sequence_Number
4321, W, 10.21,,1
4321, C,,'Payment',2
4321, C,,'From Checking Account',3
4321, D,20.00,,4
4321, C,,'Direct Deposit',4
7430, W, 40.00,,5
7430, C,,'From Checking',5

来源是一个交易账本，W代表“提款”，D代表“存款”，C代表评论。当每笔交易发生时，它都可以跟进。 0 个或更多注释行。 我想汇总“W”或“D”之后的所有 cmets，并将它们添加到“W”或“D”行。示例：

Account_Number, Code, Transaction_Amount, Comment, Sequence_Number
4321, W, 10.21,'Payment,From Checking Account',1
4321, D,20.00,'Direct Deposit',4
7430, W, 40.00,"From Checking,5

Answer 1

这是使用LEAD 和STRING_AGG 的查询。假设Withdraw 或Deposit 行的最后一个数字很大，Account_Number。

HERE 是工作代码。

SELECT *
    ,(
        SELECT STRING_AGG(comm.Comment, ', ') Comment
        FROM Transactions comm
        WHERE comm.Account_Number = a.Account_Number
            AND comm.Code = 'C'
            AND comm.Sequence_Number >= a.Sequence_Number
            AND comm.Sequence_Number < a.END_Sequence_Number
        )
FROM (
    SELECT *
        ,ISNULL(LEAD(Sequence_Number) OVER (
                PARTITION BY Account_Number ORDER BY Sequence_Number
                ), 100000000) END_Sequence_Number
    FROM dbo.Transactions t
    WHERE Code IN ('W', 'D')
    ) a

结果：

Answer 2

我会使用string_agg() 来做到这一点，但通过为每一行分配组。什么是组？非 C 代码的累积数量。所以：

select account,
       max(case when code <> 'C' then code end) as code,
       sum(amount) as amount,
       string_agg(comment, ',') within group (order by seq) as comments
from (select t.*,
             sum(case when code <> 'C' then 1 else 0 end) over (partition by account order by sequence) as grp
      from t
     ) t
group by account, grp;

Answer 3

我将此理解为一个间隙和岛屿问题，您希望在其中收集每个间隙中的所有 cmets，并将它们带到前一个岛屿。

SQL Server 没有用于字符串聚合的窗口函数，这让事情变得有点棘手。这可能是横向连接的更简单地址：

select t.account_number, t.code, t.transaction_amount, c.comment, t.sequence_number
from mytable t
outer apply (
    select top (1) t1.sequence_number as next_sequence_number
    from mytable t1
    where 
        t1.account_number = t.account_number 
        and t1.sequence_number > t.sequence_number
        and t1.code <> 'C' 
    order by t1.sequence_number
) s
outer apply (
    select string_agg(t1.comment) within group(order by t1.sequence_number) comment
    from mytable t1
    where
        t1.account_number = t.account_number 
        and t1.sequence_number > t.sequence_number
        and (
            t1.sequence_number < s.next_sequence_number 
            or s.next_sequence_number is null
        )
        and t1.code = 'C' 
) c
where t.code <> 'C'

第一个横向连接计算“下一个”非注释事务的序列号；第二个聚合当前行和下一行之间的所有 cmets。

请注意，string_agg() 仅从 SQL Server 2017 开始可用。