(1) A 表中有100条记录.

SELECT * FROM A WHERE A.COLUMN1 = A.COLUMN1

这个语句返回几条记录? (简单吧,似乎1秒钟就有答案了:)

(2) CREATE SEQUENCE PEAK_NO

SELECT PEAK_NO.NEXTVAL FROM DUAL --> 假设返回1

10秒中后,再次做

SELECT PEAK_NO.NEXTVAL FROM DUAL --> 返回多少?

(3) SQL> connect sys as sysdba

Connected.

SQL> insert into dual values ( 'Y');

1 row created.

SQL> commit;

Commit complete.

SQL> select count(*) from dual;

COUNT(*)

----------

2

SQL> delete from dual;

commit;

-->DUAL里还剩几条记录?

JUST TRY IT .