在SqlServer中使用union all 查詢兩個sql的合併結果，sql 如下

select top 1 sdtPeriod from tbfundportionassistant as p  ORDER BY p.sdtPeriod
UNION ALL
select top 1 sdtPeriod from tbfundportionassistant as p  ORDER BY p.sdtPeriod ;

執行後報錯，提示UNION ALL處有語法錯誤，查詢資料後，發現只需要排序一次即可：

select top 1 sdtPeriod from tbfundportionassistant as p  
UNION ALL
select top 1 sdtPeriod from tbfundportionassistant as p  ORDER BY p.sdtPeriod ;