兼容 Oracle sequence

​ 序列在UDB-TX Oracle兼容版本中用于生成唯一的数字序列，常用于自增ID等场景

用例

unvdb=# CREATE sequence udb_ora_sql;
CREATE SEQUENCE
unvdb=# SELECT udb_ora_sql.NEXTVAL FROM DUAL;
 nextval
---------
       1
(1 row)
unvdb=# ALTER sequence udb_ora_sql restart start with 10;
ALTER SEQUENCE
unvdb=# SELECT udb_ora_sql.NEXTVAL FROM DUAL;
 nextval
---------
       10
(1 row)
unvdb=# DROP SEQUENCE udb_ora_sql;
DROP SEQUENCE