sql嵌套更新

原地址：http://blog.csdn.net/ycb1689/article/details/43834445

方法一：

update a set HIGH=b.NEW  from SPEC1 a,tmpDOT  b
where a.high=b.old

方法二：

UPDATE A
SET HIGH=B.NEW
FROM A LEFT JOIN B ON (A.HIGH=B.OLD)

方法三：

update  a
  set high  = (select new from tmpdot where old=a.high  )
   from spec1 a