以下是dual的一些使用方法:
查看当前连接用户SQL> select user from dual;




查看当前日期、时间SQL> select sysdate from dual;
SYSDATE
----------
18-3月 -01
SQL> select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual;
TO_CHAR(SYSDATE,'YY
-------------------
2001-03-18 22:37:56
当作计算器用SQL> select 1+2 from dual;




查看序列值SQL> create sequence aaa increment by 1 start with 1;
SQL> select aaa.nextval from dual;
SQL> select aaa.nextval from dual;
NEXTVAL
----------
1
SQL> select aaa.currval from dual;
CURRVAL
----------
1