How Does Oracle query duplicate data ?, Oracle duplicate data?

How Does Oracle query duplicate data ?, Oracle duplicate data?

-Query duplicate data

Select tt. * from Table tt where custom conditions and tt. repeated field in (select t. repeated field from table t where custom condition group by t. repeated field having count (t. repeated fields)> 1)

-Query the smallest id in the duplicate data

Select tt. * from Table tt where custom conditions and tt. repeated field in (select t. repeated field from table t where custom condition group by t. repeated field having count (t. repeated fields)> 1) and tt. id in (select min (t. id) from table t where custom condition group by t. repeated field having count (t. repeated fields)> 1)