哇，union的優先順序很高嘛

原來，union的優先順序很高。比如

select stdname,[subject]='化學',化學 as score  from #student2 union all select stdname,[subject]='數學',數學 as score  from #student2 union all select stdname,[subject]='物理',物理 as score  from #student2 union all select stdname,[subject]='語文',語文 as score  from #student2 order by stdname,[subject]

等同於

select * from(select stdname,[subject]='化學',化學 as score  from #student2 union all select stdname,[subject]='數學',數學 as score  from #student2 union all select stdname,[subject]='物理',物理 as score  from #student2 union all select stdname,[subject]='語文',語文 as score  from #student2 ) as aorder by stdname,[subject]