update A set W=9 where Q=1 and W=(select top 1 W from A where Q=1)
update top (1) A set W=9 where q = 1
update A set W=9 where id=(select top 1 id from A where q=1)
update A set W=9 where Q=1 and W=2
在sqlserver中 set rowcount 1 update... 其他数据库就不知道了