sql-server - 2列のUNIONからTOP1値を取得するにはどうすればよいですか？

Question

これはクエリですが、結果から上位1つを選択するにはどうすればよいですか？これはSQLServer用です。

SELECT column1 
FROM table 
WHERE column2 = 'Whatever' AND column3 = 'Sure'

UNION

SELECT column4 
FROM table 
WHERE column2 = 'Whatever' AND column3 = 'Sure'

Answer 1

これを試して：

SELECT TOP 1 * FROM
(
  SELECT column1 FROM table WHERE column2 = 'Whatever' AND column3 = 'Sure'
  UNION
  SELECT column4 FROM table WHERE column2 = 'Whatever' AND column3 = 'Sure'
) R
ORDER BY Column1

Answer 2

試す：

SELECT max(Column) FROM (
  SELECT column1 as Column FROM table WHERE ....
  UNION 
  SELECT column4 as Column FROM table WHERE ....
)

Answer 3

意味ですか

SELECT TOP 1 * 
FROM (
    SELECT column1 FROM table WHERE column2 = 'Whatever' AND column3 = 'Sure'
    UNION
    SELECT column4 FROM table WHERE column2 = 'Whatever' AND column3 = 'Sure')