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SQL> select * from t1;
        ID        AGE
---------- ----------
         1         20
         2         19
         3         19
         4         21
         5         22
         6         27
6 rows selected.
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SQL> select t11.*
  2  from t1 t11
  3  where 2=(select count(*) from t1 t22 where t11.age>t22.age);
        ID        AGE
---------- ----------
         1         20
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SQL> select id,age
  2  from
  3  (
  4  select id,age,
  5  dense_rank() over(order by age) dr
  6  from t1
  7  )
  8  where dr=3;
        ID        AGE
---------- ----------
         4         21
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SQL> select id,age
  2  from
  3  (
  4  select id,age,
  5  rank() over(order by age) dr
  6  from t1
  7  )
  8  where dr=3;