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?Oracle??????????????????????????????????????????????????Oracle????????????????
create table student( studentid int primary key not null, studentname varchar(8), age int);
alter table??????????????????alter table student rename column oldcolumn to newcolumn;
???
alter table student add column newcolumn varchar(10);
drop table???drop table student;
insert into????????????????insert into student values(2, 'bbb', 13);
delete from???????????????delete from student;
truncate table???truncate table student;
alter table???????????????????alter table student drop constraint yy;
add constraint??????alter table student add constraint pk_students primary key (studentid);
?Oracle???????????????????????????????
alter table emp add constraint fk_emp_dept foreign key (dept) references dept(deptno) on delete cascade;
??
alter table emp add constraint fk_emp_dept foreign key (dept) references dept(deptno) on delete set null;
?Oracle??????to_date????????????
insert into student values('ss12', to_date('21-08-2010 12:21:11', 'DD-MM-YYYY HH:MI:SS')); ????????????????????ORA-01407:????NULL??????????????????????????NULL????????on delete cascade?on delete set null????
?????????????????????????
create table dept( deptno number(10) not null, deptname varchar2(30) not null, constraint pk_dept primary key (deptno));create table emp( empno number(10) not null, fname varchar2(20), lname varchar2(20), dept number(10), constraint pk_emp primary key (empno));alter table emp add constraint fk_emp_dept foreign key (dept) references dept(deptno) on delete cascade;insert into dept values(1, '???');insert into dept values(2, '???');insert into emp values(2, 'Mary', 'Song', 1);insert into emp values(3, 'Linda', 'Liu', 2);insert into emp values(4, 'Linlin', 'Zhang', 1);
on delete????????????????????Oracle?????????
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