You can find the SQL ID for a statement by querying v$sql:

select /* this */* from dual;
select /* that */* from dual;

select sql_id, sql_text from v$sql
where  ( sql_text like '%this%' or sql_text like '%that%' )
and    sql_text not like '%not this%';

SQL_ID        SQL_TEXT                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
------------- ----------------------------
gqrwquv0utrb7 select /* this */* from dual                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
cd8h6juhw5wkk select /* that */* from dual

This view also contains some metrics such as elapsed time, cpu time, buffer gets, etc. There are several other views that contain further performance stats such as v$sqlstats.

The SQL ID is a hash of the statement's text. So there will only ever be one ID for a given statement. But one statement can have two or more different plans. These will have different plan_hash_values. You can encourage/force Oracle Database to use a particular plan with SQL Plan Management (SPM). This uses features such as SQL profiles and baselines to do this.

Read more about this at:

http://www.oracle.com/technetwork/database/bi-datawarehousing/twp-sql-plan-management-11gr2-133099.pdf
http://www.oracle.com/technetwork/database/bi-datawarehousing/twp-sql-plan-mgmt-12c-1963237.pdf