左外连接查询极慢 - SQL Server

Question

SQL Server 查询的大问题！

所以下面的查询在查询中使用了 JOIN 命令，但运行时间不少于 15-20 分钟！不知道如何更好地优化这段代码:(

关于如何解决此问题的任何想法？

SELECT dbo.DB_Timetrack.[JOB #], dbo.DB_Timetrack.[Last Name], dbo.DB_Timetrack.[First Name], dbo.DB_Timetrack.HOURS, dbo.DB_Timetrack.BEGDATE, dbo.DB_Timetrack.LOCATNID, 
                         dbo.DB_Timetrack.DESCR, dbo.DB_Timetrack.CODE, dbo.DB_Timetrack.TYPE, 
                         CASE WHEN dbo.DB_Job_status_open_and_closed.WS_Job_Number != '' THEN dbo.DB_Timetrack.Hours ELSE 0 END AS HoursWon, dbo.DB_Timetrack.NUMBERONLY, 
                         dbo.DB_Job_status_open_and_closed.WS_Job_Number_Only, dbo.DB_Job_status_open_and_closed.CREATDDT, DATEDIFF(Day, dbo.DB_Timetrack.BEGDATE, 
                         dbo.DB_Job_status_open_and_closed.CREATDDT) AS Date_Difference, DBCRM_MSCRM.dbo.DB_Opportunity_SalespersonID.new_GPSalespersonName, 
                         CASE WHEN DBCRM_MSCRM.dbo.DB_Opportunity_SalespersonID.new_GPSalesRepCode <> '' THEN DBCRM_MSCRM.dbo.DB_Opportunity_SalespersonID.new_GPSalesRepCode ELSE dbo.DB_Job_status_open_and_closed.Salesperson
                          COLLATE Latin1_General_CI_AI END AS SalespersonID

FROM            dbo.DB_Timetrack LEFT OUTER JOIN
                         DBCRM_MSCRM.dbo.DB_Opportunity_SalespersonID ON dbo.DB_Timetrack.NUMBERONLY COLLATE Latin1_General_CI_AI = DBCRM_MSCRM.dbo.DB_Opportunity_SalespersonID.Job_Num_Only LEFT OUTER JOIN
                         dbo.DB_Job_status_open_and_closed ON dbo.DB_Timetrack.NUMBERONLY = dbo.DB_Job_status_open_and_closed.WS_Job_Number_Only

WHERE        (dbo.DB_Timetrack.HOURS > 0) AND (dbo.DB_Timetrack.DESCR <> '') AND (dbo.DB_Timetrack.BEGDATE > CONVERT(DATETIME, '2013-01-01 00:00:00', 102))

任何建议将不胜感激！

Answer 1

这基本上是您的查询：

SELECT . . .
FROM dbo.DB_Timetrack LEFT OUTER JOIN
     DBCRM_MSCRM.dbo.DB_Opportunity_SalespersonID
     ON dbo.DB_Timetrack.NUMBERONLY COLLATE Latin1_General_CI_AI = DBCRM_MSCRM.dbo.DB_Opportunity_SalespersonID.Job_Num_Only LEFT OUTER JOIN
     dbo.DB_Job_status_open_and_closed
     ON dbo.DB_Timetrack.NUMBERONLY = dbo.DB_Job_status_open_and_closed.WS_Job_Number_Only
WHERE (dbo.DB_Timetrack.HOURS > 0) AND
      (dbo.DB_Timetrack.DESCR <> '') AND
      (dbo.DB_Timetrack.BEGDATE > CONVERT(DATETIME, '2013-01-01 00:00:00', 102))

1.) 首先，排序规则可能会扼杀索引的任何使用。

2.) 您需要确保在 DB_Job_status_open_and_closed(WS_Job_Number_Only) 和 DB_Opportunity_SalespersonID(Job_Num_Only) 上有索引。

3.) 您可能还会发现DB_Timetrack(BEGDATE, HOURS, DESCR, NumberOnly) 上的索引会有所帮助（如果您真的使用 SQL Server，最后三列可以只是 include）。