SQL 存储过程中多个更新语句运行缓慢

Question

请参考以下 SQL 命令，它是存储过程的一部分。存储过程创建一个名为#TREPORT 的临时表，然后我对 SODATE 列执行以下多次更新。

临时表 (#TREPORT) 有大约 100 万条记录，以下语句使性能变慢。我该如何进一步改进它？

@SDATE 和@EDATE 是参数，分别是开始日期和结束日期。

提前致谢。

   UPDATE #TREPORT SET 
          SODATE  = '1900-01-01 00:00:00.000' where #TREPORT.SODATE is NULL

   UPDATE #TREPORT SET 
          SODATE  = (SELECT TOP 1 docdate from SO200 
          where SO200.NUMBORIG = #TREPORT.SOPNr 
          AND SO200.SOTYPE = '3' 
    --         AND 
    --DOCDATE is not null and DOCDATE >= '' +CONVERT(varchar(10),@SDATE,101) +''
    --         and DOCDATE <= '' +CONVERT(varchar(10),@EDATE,101) +''
      ) 
          where #TREPORT.SODATE = '1900-01-01 00:00:00.000' or #TREPORT.SODATE is NULL

   UPDATE #TREPORT SET 
          SODATE  = (SELECT TOP 1 docdate from SO100 
          where SO100.NUMBORIG = #TREPORT.SOPNr 
          AND SO100.SOTYPE = '3' 
    --         AND 
    --DOCDATE is not null and DOCDATE >= '' +CONVERT(varchar(10),@SDATE,101) +''
    --         and DOCDATE is not null and DOCDATE <= '' +CONVERT(varchar(10),@EDATE,101) +''
      ) 
      where #TREPORT.SODATE = '1900-01-01 00:00:00.000'  or #TREPORT.SODATE is NULL

   UPDATE #TREPORT SET 
          RowValue = 'C' where 
      (#TREPORT.SODATE < '' +CONVERT(varchar(10),@SDATE,101) +''
          or #TREPORT.SODATE > '' +CONVERT(varchar(10),@EDATE,101) +'')

   UPDATE #TREPORT SET 
          RowValue = 'D' where #TREPORT.SODATE  = '1900-01-01 00:00:00.000' 
          or #TREPORT.SODATE is NULL

Answer 1

大型更新最好分批执行。在此处查看解决方案：

http://www.sqlusa.com/bestpractices/largeupdate/

至于合并您的更新，您的第一次更新完全是多余的，因为您将 NULL 替换为默认值，而其他更新替换“NULL 或 {默认值}”，因此您可以跳过第一个完全。

其他 4 个更新可以通过 CASE 语句合并为一个。

UPDATE #TREPORT SET SODATE=CASE
  WHEN EXISTS(SELECT * from SO200 where SO200.NUMBORIG = #TREPORT.SOPNr AND SO200.SOTYPE = '3')
    THEN (SELECT TOP 1 docdate from SO200 
          where SO200.NUMBORIG = #TREPORT.SOPNr 
          AND SO200.SOTYPE = '3')
  WHEN EXISTS(SELECT * from SO100 where SO100.NUMBORIG = #TREPORT.SOPNr AND SO100.SOTYPE = '3')
    THEN (SELECT TOP 1 docdate from SO100 
          where SO100.NUMBORIG = #TREPORT.SOPNr 
          AND SO100.SOTYPE = '3')
  ELSE '1900-01-01 00:00:00.000' 
END
,  RowValue=CASE
  WHEN       (#TREPORT.SODATE < '' +CONVERT(varchar(10),@SDATE,101) +''
          or #TREPORT.SODATE > '' +CONVERT(varchar(10),@EDATE,101) +'')
    THEN 'C'
  ELSE 'D'
END
where #TREPORT.SODATE = '1900-01-01 00:00:00.000' or #TREPORT.SODATE is NULL