Solutions for INSERT OR UPDATE on SQL Server

未验证，有时间改改再说

begin tran 
if exists(select* fromtable with(updlock,serializable)where key= @key) 
begin 
   update tableset ... 
   where key= @key 
end 
else 
begin 
   insert table(key,...) 
   values (@key,...) 
end 
commit tran 

or

begin tran     update table with (serializable) set ...     where kay = @key       if @@rowcount = 0     begin            insert table (key, ...) values (@key,..)     end  commit tran  
MS Sql2008 introduces merge from the SQL:2003 standard:
merge tablename WITH(HOLDLOCK) as target  using (values ('new value', 'different value'))      as source (field1, field2)      on target.idfield = 7  when matched then      update      set field1 = source.field1,          field2 = source.field2,          ...  when not matched then      insert ( idfield, field1, field2, ... )      values ( 7,  source.field1, source.field2, ... )  

 另外参考http://www.mssqltips.com/sqlservertip/1704/using-merge-in-sql-server-to-insert-update-and-delete-at-the-same-time/