Oracle 11g Release 2

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create table ds1 ( col1, col2 ) AS
  select 'A', 1 from dual
  union all select 'B', 2 from dual
  union all select 'C', 3 from dual
  union all select 'D', 4 from dual
  union all select 'E', 4 from dual
  union all select 'F', 10 from dual;
6 rows affected

SELECT MIN( col1 ) KEEP ( DENSE_RANK FIRST ORDER BY col2 ) AS col1
FROM   ds1


COL1


A


SELECT col1, col2
FROM   (
  SELECT ds1.*,
         DENSE_RANK() OVER ( ORDER BY col2 ASC ) AS rnk
  FROM   ds1
)
WHERE  rnk = 1


COL1
COL2


A
1