Question

创建SQL查询以汇总一些数据。它很慢，所以我想我会请求一些帮助。

表是一个包含以下内容的日志表：

loc, tag, entrytime, exittime, visits, entrywt, exitwt

我的测试日志中有700,000条记录。 entrytime和exittime是时代价值。

我知道我的查询效率很低，因为它在表格中翻了4次。

select 
    loc, edate, tag,
    (select COUNT(*) from mylog as ml 
     where mvlog.loc = ml.loc 
       and mvlog.edate = CONVERT(date, DATEADD(ss, ml.entrytime, '19700101')) 
       and mvlog.tag = ml.tag) as visits,
    (select SUM(entrywt - exitwt) from mylog as ml2 
     where mvlog.loc = ml2.loc 
       and mvlog.edate = CONVERT(date, DATEADD(ss, ml2.entrytime, '19700101')) 
       and mvlog.tag = ml2.tag) as consumed,
    (select SUM(exittime - entrytime) from mylog as ml3 
     where mvlog.loc = ml3.loc 
       and mvlog.edate = CONVERT(date, DATEADD(ss, ml3.entrytime, '19700101')) 
       and mvlog.tag = ml3.tag) as occupancy
from 
    eventlogV as mvlog with (INDEX(pt_index))

索引pt_index由列tag和loc组成。

当我运行此查询时，它在大约30秒内完成。由于我的查询效率低下，我相信它会更好。

任何想法都赞赏。

Answer 1

好像你可以将mOLLog LEFT JOIN加入eventlogV一次并得到相同的结果。

SELECT  mvlog.loc,
        mvlog.edate,
        mvlog.tag,
        COUNT(ml.loc) AS visits,
        SUM(entrywt - exitwt) AS consumed,
        SUM(exittime - entrytime) AS occupancy
FROM    eventlogV AS mvlog
        LEFT OUTER JOIN mylog ml ON mvlog.loc = ml.loc
                                    AND mvlog.edate = CONVERT(DATE,DATEADD(ss,ml.entrytime,'19700101'))
                                    AND mvlog.tag = ml.tag
GROUP BY mvlog.loc,
        mvlog.edate,
        mvlog.tag

优化我的T-SQL查询以提高性能

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