使排名查询高效 [英] Making the ranking query efficient

问题描述

我在ACCESS 2010中使用以下代码对表中的〜30000行进行排名.但是，排名大约需要15分钟(我必须再进行5列才能完成排名，而这很容易花费一个多小时).我需要这些列以进行进一步处理，因此尝试创建一个新表.我也尝试过追加和更新现有表.一切都需要相同的时间.我在这里遗漏了一些明显的东西可以使它更快地工作吗?

I am using the following code in ACCESS 2010 to rank ~30000 rows from a table. However it takes around 15 minutes to do the ranking (I have to do this for 5 more columns and it could easily take more than an hour). I need these columns for further processing and hence tried creating a new table. I have also tried appending and updating to existing tables. Everything takes the same time. Am I missing something obvious here that could make it work faster?

SELECT MasterTable.Sales, (SELECT Count(*)+1 as HowMany From MasterTable AS Dupe WHERE Dupe.Sales > MasterTable.Sales) AS SalesRank INTO tableRank FROM MasterTable;

SELECT MasterTable.Sales, (SELECT Count(*)+1 as HowMany From MasterTable AS Dupe WHERE Dupe.Sales > MasterTable.Sales) AS SalesRank INTO tableRank FROM MasterTable;

MasterTable的详细信息: 11列. 1个主键(文本). 5个参数(Sales SalesQty Profit Hits Cost，全数字). 5个参数的等级(例如SalesRank等) 30,000行

Details on the MasterTable: 11 columns. 1 primary key (Text). 5 parameters (Sales SalesQty Profit Hits Cost, all numeric). Ranks of 5 parameters(like SalesRank and so on) 30,000 rows

推荐答案

您尝试使用分组左联接吗?

Did you try a left join with grouping?

SELECT
    m1.Sales,
    COUNT(*) AS HowMany
FROM
    MasterTable AS m1
    LEFT JOIN MasterTable m2 ON m1.Sales <= m2.Sales
GROUP BY
    m1.Sales

这篇关于使排名查询高效的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！