这句UPDATE的SQL该怎么写？
1、表   CompanyBgt   的数据结构是这样的：
fyearmonth   branchid   categoryid   oborrb  
其中，fyearmonth   branchid   categoryid为主健
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2、我需要把这张表中，fyearmonth从200704到200803的，channelid为“IT”的OBRORB数据全部替换成channelid是“DPIT”的数据   ？
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3、我试着写了一下，不知道是否正确，请各位看一下：
UPDATE   CompanyBgt   a
      SET   a.oborrb   =(select   oborrb   from   CompanyBgt   b   where  
            a.fyearmonth   =b.fyearmonth
            and   a.branchid=b.branchid
            and   a.categoryid=b.categoryid
      and     b.channelid   =   'DPIT '   and   a.channelid= 'IT ')
where   a.channelid= 'IT '   and   a.Fyearmonth> = '200704 '   and   a.Fyearmonth <= '200803

------解决方案--------------------
可以用關聯寫


Update A Set OBRORB = B.OBRORB
From CompanyBgt A
Inner Join CompanyBgt B
On A.Fyearmonth = B.Fyearmonth And A.branchid = B.branchid And A.categoryid = B.categoryid
Where A.channelid = 'IT ' And B.channelid = 'DPIT ' And A.Fyearmonth Between '200704 ' And '200803 '
------解决方案--------------------

update CompanyBgt set CompanyBgt.oborrb = c.oborrb from (select * from CompanyBgt b where b.channelid = 'DPIT ') c,CompanyBgt where
c.fyearmonth =CompanyBgt.fyearmonth
and c.branchid=CompanyBgt.branchid
and c.categoryid=CompanyBgt.categoryid
and CompanyBgt.channelid = 'IT ' and CompanyBgt.Fyearmonth between '200704 'and '200803 '