Bagaimana cara memeriksa nomor yang hilang dari serangkaian angka?

Solusi tanpa hardcoding 9:

select min_a - 1 + level
     from ( select min(a) min_a
                 , max(a) max_a
              from test1
          )
  connect by level <= max_a - min_a + 1
    minus
   select a
     from test1

Hasil:

MIN_A-1+LEVEL
-------------
         7003
         7007
         7008
         7009

4 rows selected.