问题的SQL Server查询

我有以下查询其运行缓慢：问题的SQL Server查询

WITH AcdTran 
    AS (select SequenceNo, 
       ReqID, 
       PolNumber, 
       transaction_id, 
       application_data, 
       trans_type, 
       retries, 
       status, 
       direction 
     from dbo.acord_transaction_benchmark with (nolock) 
     where direction = 'OUT') 
select top 1 * 
from AcdTran a 
where a.transaction_id = (select top 1 transaction_id 
          from AcdTran b 
          where b.PolNumber = a.PolNumber 
          order by ReqID, 
            SequenceNo, 
            transaction_id) 
     and (status = 'New' 
       or status = 'Resubmit') 
     and retries > 0

我如何优化呢？跑得更快？

谢谢

来源

2011-08-30 JustMe

什么是它应该做的？你的'select top 1 *'缺少一个'order by' –

它应该按顺序选择一个新的状态为New或重新提交的记录。所以，如果我有2个记录的某个PolNumber，并且1有序列1，另一个有序列2，它应该选取序列1的那个。 – JustMe

好吧，这只是一个标准的“最大n个每组”查询，然后我认为。有3种方法[在此评估]（http://www.sqlmag.com/article/departments/optimizing-top-n-per-group-queries）。最好的使用取决于你的索引和数据分布。 –

应与窗口函数ROW_NUMBER更快：

WITH AcdTran AS (
     SELECT SequenceNo, 
       ReqID, 
       PolNumber, 
       transaction_id, 
       application_data, 
       trans_type, 
       retries, 
       status, 
       direction, 
       ROW_NUMBER() OVER(PARTITION BY transaction_id ORDER BY ReqID, SequenceNo, transaction_id) N 
      FROM dbo.acord_transaction_benchmark with (nolock) 
      WHERE direction = 'OUT') 
SELECT * 
    FROM AcdTran 
WHERE (status = 'New' 
      OR status = 'Resubmit') 
     AND retries > 0 
     AND N = 1;

由于我没有你的表结构也没有任何数据，我明明没有测试，所以你可能要修改查询一下，但你有想法。

来源

2011-08-30 22:01:44

好吧，这是返回，多个记录。我只需要1条记录.. – JustMe

@JustMe - 你能否提供一些示例数据和期望的结果。 –

JustMe：我的错误，它应该是'分区由transaction_id'，我编辑我的帖子。 –

如果你拿出你的子查询转换为连接：

WITH AcdTran 
    AS (select SequenceNo, 
       ReqID, 
       PolNumber, 
       transaction_id, 
       application_data, 
       trans_type, 
       retries, 
       status, 
       direction 
     from dbo.acord_transaction_benchmark with (nolock) 
     where direction = 'OUT') 
select top 1 * 
from AcdTran a 
inner join AcdTran b on a.SequenceNo = b.SequenceNo --or whatever the PK is 
where a.transaction_id = b.transaction_id and 
     a.PolNumber = b.PolNumber and 
     (a.status = 'New' or a.status = 'Resubmit') and 
     a.retries > 0 
order by b.ReqID, 
     b.SequenceNo, 
     b.transaction_id

来源

2011-08-30 22:05:18 davecoulter

问题的SQL Server查询

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