21建立班级表
CREATE TABLE class(
classId NUMBER(2),
cName VARCHAR2(40)
);
insert into class values(001,’计算机科学与技术’);
insert into class values(002,’计算机科学与技术’);
insert into class values(003,’计算机科学与技术’);
insert into class values(004,’计算机科学与技术’);
insert into class values(005,’财务管理’);
insert into class values(006,’财务管理’);
insert into class values(007,’会计专业’);
insert into class values(008,’会计专业’);
22
alter table class add(name varchar(20));
UPDATE class SET name = ‘歌谣’ WHERE classid = ‘1’;
UPDATE class SET name = ‘歌谣’ WHERE classid = ‘2’;
UPDATE class SET name = ‘歌谣’ WHERE classid = ‘3’;
UPDATE class SET name = ‘歌谣’ WHERE classid = ‘4’;
UPDATE class SET name = ‘歌谣’ WHERE classid = ‘5’;
UPDATE class SET name = ‘歌谣’ WHERE classid = ‘6’;
UPDATE class SET name = ‘歌谣’ WHERE classid = ‘7’;
UPDATE class SET name = ‘歌谣’ WHERE classid = ‘8’;
23 select name from student union all select name from class;
–Union：对两个结果集进行并集操作，不包括重复行，同时进行默认规则的排序；
–Union All：对两个结果集进行并集操作，包括重复行，不进行排序；
24在两个表中查找共同行
create view E
as
select xh,sex,name from student
where name=’歌谣’
select * from E
25从一个表中查找另一个表中没有的值
select name from student
minus
select name from class–查找class中没有的行
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