Session Level Sequences no Oracle Database: Produzindo valores únicos dentro de uma sessão

SQL> CREATE SEQUENCE sequence_teste
  START WITH   1
  INCREMENT BY 1
  SESSION

Sequence created.</span>

CREATE GLOBAL TEMPORARY TABLE tabela_teste (
   id  NUMBER DEFAULT sequence_teste.nextval NOT NULL
  ,first_name VARCHAR2(20)
  ,last_name VARCHAR2(25)
  )
  ON COMMIT PRESERVE ROWS
/

Table created.

INSERT INTO tabela_teste (first_name, last_name)
SELECT first_name, last_name
FROM hr.employees
WHERE rownum < 6
/

5 rows created.

SELECT *
 FROM tabela_teste
 /

EMPLOYEE_ID FIRST_NAME           LAST_NAME</span>
----------- -------------------- -------------------------
         1 Joao                 Silva
         2 Andre                Silva
         3 Pedro                Silva
         4 Mario                Silva
         5 Fulano               Silva

INSERT INTO tabela_teste (first_name, last_name)
SELECT first_name, last_name
FROM hr.employees
WHERE rownum < 10
/

9 rows created.

SELECT *
 FROM tabela_teste
 /

EMPLOYEE_ID FIRST_NAME           LAST_NAME
----------- -------------------- -------------------------
         1 Joao                 Silva
         2 Andre                Silva
         3 Pedro                Silva
         4 Mario                Silva
         5 Fulano               Silva
         6 Ciclano              Silva
         7 Beltrano             Silva
         8 Jose                 Silva
         9 Alex                 Silva

SQL> ALTER SEQUENCE … GLOBAL;

SQL> ALTER SEQUENCE … SESSION;