union all中使用order by子查詢時需將含order by的子查詢包在一個不含order by的查詢裡再進行union all。

否則會報“Incorrect usage of UNION and ORDER BY”

例如：

1.錯誤用法：

           select id from test1 order by id

           union all

           select id from test2 order by id

2.正確用法：

           select * from (select id from test1 order by id) t1

           union all

           select * from (select id from test2 order by id) t2