Question

我正在构建的这个MS Access查询非常慢。我只测试一个月的数据（一个表驱动这个查询，有28,577条记录，36列）。

以下是我要完成的事情：

我想按模型返回以特定交易类型出售的独特车辆的数量（此数据库未规范化，并且是从加载到表格中的Excel工作表构建的）。

存在第一个子查询，因为我理解在Access中您不能将DISTINCT语句与聚合函数一起使用。所以我需要构建一个子查询来处理Count（DISTINCT VIN）。

第二个子查询是我认为的罪魁祸首。每个VIN可能有许多条目。例如，车辆可能已经使用我正在计算的交易类别之一，然后取消，并转售到我不想计算的交易类别之一。这将为此VIN生成三条记录：

销售到我认为我想要计算的交易类别
取消首次销售
转售为我不想算的交易类别

第二个子查询检查VIN是否有“已取消的销售”记录，然后不包括计数中的第一个Sale。

希望我能很好地解释这一点，并且有人可以为我提供一个加速查询的潜在解决方案。

感谢

查询

PARAMETERS [Enter Sales Month Start Date] DATETIME, [Enter Sales Month End Date] 
DATETIME; 

SELECT DSTNCT_COUNT.trans      AS Trans, 
       DSTNCT_COUNT.mdl        AS Model, 
       Count(DSTNCT_COUNT.cnt) AS VIN_COUNT 
FROM   (SELECT DISTINCT new_bbss.vin              AS cNt, 
                        new_bbss.[model category] AS MDL, 
                        new_bbss.[trans category] AS Trans 
        FROM   new_bbss 
        WHERE  ( ( ( new_bbss.[trans category] ) NOT LIKE 'Individual' 
                   AND ( new_bbss.[trans category] ) NOT LIKE 'Corporate' 
                   AND ( new_bbss.[trans category] ) NOT LIKE 'Cancel' 
                   AND ( new_bbss.[trans category] ) NOT LIKE 'Partners' 
                   AND ( new_bbss.[trans category] ) NOT LIKE 'Special' 
                   AND ( new_bbss.[trans category] ) NOT LIKE 'Employee' 
                   AND ( new_bbss.[trans category] ) NOT LIKE 'Mobile' 
                   AND ( new_bbss.[trans category] ) NOT LIKE 'JLR FLEET' ) 
                   AND ( ( new_bbss.[retailer code] ) LIKE 'R*' ) ) 
                   AND new_bbss.[trans date] BETWEEN [enter sales month start date] 
                                             AND 
                                                 [enter sales month end date] 
                   AND new_bbss.vin NOT IN(SELECT new_bbss.vin 
                                           FROM   new_bbss 
                                           WHERE  new_bbss.[trans category] LIKE 
                                              'CancelVIP*' 
                                               OR new_bbss.[trans category] LIKE 
                                                  'CancelDealer Local*' 
                                               OR new_bbss.[trans category] LIKE 
                                                  'CancelLoaner*' 
                                               OR new_bbss.[trans category] LIKE 
                                                  'CancelAlive*'))
       AS DSTNCT_COUNT 
GROUP  BY trans, mdl;

Answer 1

对于NOT IN，MsAccess应该比在NOT EXISTS上慢。我不知道这是否属实，但无论如何你都可以尝试。此外，您可以将此限制从WHERE子句移动到HAVING子句，因为vin在GROUP BY子句中。这可能会减少MsAccess查看的时间。

select [model category], [trans category], count(*)
from
(
  select [model category], [trans category], vin
  from new_bbss
  where [trans category] not like 'Individual' 
    and [trans category] not like 'Corporate' 
    and [trans category] not like 'Cancel' 
    and [trans category] not like 'Partners' 
    and [trans category] not like 'Special' 
    and [trans category] not like 'Employee' 
    and [trans category] not like 'Mobile' 
    and [trans category] not like 'JLR FLEET' 
    and [retailer code] like 'R*'
    and [trans date] between [enter sales month start date] 
                         and [enter sales month end date] 
  group by [model category], [trans category], vin
  having not exists
  (
    select *
    from new_bbss unwanted
    where unwanted.vin = new_bbss.vin
    and  
    (    unwanted.[trans category] like 'CancelVIP*' 
      or unwanted.[trans category] like 'CancelDealer Local*' 
      or unwanted.[trans category] like 'CancelLoaner*' 
      or unwanted.[trans category] like 'CancelAlive*'
    )
  )
) matches
group by [model category], [trans category];

BTW：应该有一个关于vin的索引，所以MsAccess可以快速查找其记录。

优化MS Access Double SubQuery

查询

1 个答案: