整个表的数据列出来的有关问题

整个表的数据列出来的问题？
求一SQL：
我想将整个表的数据列出来，tabletemp表中有id,flag,a,b,c,f字段,如果 flag='是' 执行 select a,b,b+c from tabletemp 如果flag='否' 执行 select a,b,b+f from tabletemp 列出全部表中的tabletemp中的数据并按id排序，这个语句怎么写？

[解决办法]
select a,b,b+c from tabletemp where flag = '是'
union all
select a,b,b+f from tabletemp where flag = '否'

[解决办法]

SQL code

select a , b , newcol = b+c from tabletemp where flag = '是' union  all select a , b , newcol = b+f from tabletemp where flag = '否'order by id
[解决办法]
select   a,b,b+c   from   tabletemp where flag='是'  
union
select   a,b,b+c   from   tabletemp flag='否'  
order by id
[解决办法]
SQL code
--一共三个,你看哪个合适?select a , b , newcol from(  select id , a , b , newcol = b+c from tabletemp where flag = '是'   union  all   select id , a , b , newcol = b+f from tabletemp where flag = '否') torder by id
[解决办法]
select a , b , newcol = b+ case when flag = '是' then c else f end
from tabletemp
[解决办法]
select a , b , newcol = b+ case when flag = '是' then c else f end
from tabletemp
order by id