帮忙看看这个UPDATE语句问题么？

winfly

Update YB_SCMX a Set a.dj = (Select b.dj From YW_ZYFYMX b Where a.zyh = b.zyh and a.xmbm = b.xmbm and a.dh = b.dh and to_date(a.rq)  = b.rq);

为什么总是提示SQL error -201 : A Syntax error has occurred

请帮忙，谢谢

ivhb

Update YB_SCMX Set dj = (
  Select b.dj
  From YW_ZYFYMX b
  Where YB_SCMX.zyh = b.zyh
  and YB_SCMX.xmbm = b.xmbm
  and YB_SCMX.dh = b.dh
  and to_date(YB_SCMX.rq)  = b.rq
);

关联子查询的update/delete, 主表不能用别名