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Oracle???????

1. ?????

????????????????????Oracle????????????????????????????????????????

1.1 ?????

sqlplus / as sysdbaalter user system account unlock;alter user scott identified by tiger;grant resource, connect to scott;

1.2 ????

• number ? number(18,2)??????????number(18,2) ????????
• nvarchar2(20) ? varchar2(20)???????????????
• date ? timestamp??????????????
• nclob?lob ? blob???????????nclob ???????????

2. ?????

2.1 ????

create table t_student (    studentid number,    name varchar2(20) not null,    sex number,    birthday date,    age number,    classnum number,    primary key (studentid));

2.2 ????

alter table t_student add constraint fk_student_classnum     foreign key (classnum) references t_class (classnum);

3. SQL??

3.1 ????

insert into t_student    (studentid, name, sex, birthday, age, classnum)values    (4, '???', 0, to_date('1990/08/08', 'yyyy/mm/dd'), 27, 1);

3.2 ????

delete from t_student where studentid = 4;

3.3 ????

update emp set sal = sal + 200; -- ????update emp set sal = sal - 200, comm = 3000; -- ???????update emp set comm = comm * 2 where job = 'CLERK'; -- ????

3.4 ????

select * from emp where job in ('CLERK', 'SALESMAN') and ename like '%S%';

4. ??????

4.1 ??????

select substr(e.ename, 1, 2) from emp e where e.ename like '%S%';

4.2 ??????

select instr('hello world', 'o', -9) from dual;

5. ?????

5.1 ????

create index idx_ename on emp (ename);

5.2 ????

select * from emp where ename like '%S%' and sal > 1000;

6. ????

create sequence seq_student    minvalue 1    maxvalue 1000000    start with 1    increment by 1    cycle;insert into t_student values (seq_student.nextval, '???', 0, sysdate, 1, 15);

7. ????

7.1 ????

select e.ename from emp e where e.ename like '%??%';

7.2 ??????

to_date('1990/08/08', 'yyyy/mm/dd');

?????????? Oracle?????????????????