Oracle: Resetting an identity column vs resetting a sequence
Given that identity column internally uses a sequence, why is it not possible to do the same with a sequence i.e. change its start value to a specific number with a single alter statement?


Oracle Official way of resetting a sequence is dropping and recreating the sequence, of course, you need to take care about the privileges granted. 


  You can also use this statement to restart a sequence by dropping and then re-creating it. For example, if you have a sequence with a current value of 150 and you would like to restart the sequence with a value of 27, then you can drop the sequence and then re-create it with the same name and a START WITH value of 27.


Oracle 12c Docs

However, there is an undocumented way to reset the sequence which works for Oracle 12c. 

SQL&gt; select serial.nextval from dual;

   NEXTVAL
----------
         4

SQL&gt; alter sequence serial restart start with 1;

Sequence altered.

SQL&gt;  select serial.nextval from dual;

   NEXTVAL
----------
         1