Search notes:

Oracle: Query last executed SQL statement by joining V$SESSION and V$SQL

V$SESSION stores the hash and the child number of the most recently executed SQL statement in prev_hash_value and prev_child which allows the query the text, SQLID etc. from V$SQL: 
select
   sql.sql_id,
   sql.sql_text
from
   v$session ses                                                     join
   v$sql     sql on ses.prev_hash_value   = sql.hash_value    and
                    ses.prev_child_number = sql.child_number        
where
   ses.sid = sys_context('userenv', 'sid')
;

Using concept in SQL*Plus

SQL> set  serveroutput off
SQL> var  sqlid varchar2(13)
SQL> select 'an sql statement' from dual;
SQL> -- TODO child number should also be captured.
SQL> exec    select sql.sql_id into :sqlid from v$session ses join v$sql sql on ses.prev_hash_value = sql.hash_value and ses.prev_child_number = sql.child_number where ses.sid = sys_context('userenv', 'sid')
SQL> select  sql_text from v$sqlarea where sql_id = :sqlid;
SQL> select * from table(dbms_xplan.display_cursor(:sqlid));
… but see also the _sql_id predefined variable …

Index