(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 .
责任编辑：小草
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