--版本是SQL2000
--数据量都不大，几万条，但是执行非常慢，要几分钟。。
--怎么优化呢
UPDATE T_BASE_PARTSALF SET CURRSALF = T1.SAFENUM,
                        UPDATETIME=ISNULL(CONVERT(DATETIME,T1.UPDATETIME),GETDATE()),
                        UPDATEMAN='SYSMAN'
              FROM (
SELECT IOSF.SAFENUM,IOSF.UPDATETIME,PART.PARTID,FACT.FACTID FROM T_IO_SAFESTORAGE IOSF
LEFT JOIN T_BASE_PART PART ON IOSF.PARTCODEU8=PART.PARTCODE
LEFT JOIN T_BASE_FACT FACT ON IOSF.FACTCODE=FACT.FACTCODE
WHERE ISACTIVE=1) AS T1
                        WHERE T_BASE_PARTSALF.PARTID = T1.PARTID AND T_BASE_PARTSALF.FACTID=T1.FACTID
 

;WITH T
AS(
SELECT IOSF.SAFENUM,IOSF.UPDATETIME,PART.PARTID,FACT.FACTID FROM T_IO_SAFESTORAGE IOSF
LEFT JOIN T_BASE_PART PART ON IOSF.PARTCODEU8=PART.PARTCODE
LEFT JOIN T_BASE_FACT FACT ON IOSF.FACTCODE=FACT.FACTCODE
WHERE ISACTIVE=1
)
UPDATE T_BASE_PARTSALF SET CURRSALF = T.SAFENUM,
                        UPDATETIME=ISNULL(CONVERT(DATETIME,T1.UPDATETIME),GETDATE()),
                        UPDATEMAN='SYSMAN'
              FROM T WHERE T_BASE_PARTSALF.PARTID = T1.PARTID 
AND T_BASE_PARTSALF.FACTID=T1.FACTID

这样试试，还有where后面的字段加索引