--------------------对表的操作-------------------------- --
创建表
create table classes ( id number(9) not null primary key,
classname varchar2(40) not null )
--查询表 select * from classes;
--删除表 drop table students;
--修改表的名称 rename alist_table_copy to alist_table;
--显示表结构 describe test --不对没查到
-----------------------对字段的操作----------------------------------- --
增加列 alter table test add address varchar2(40);
--删除列 alter table test drop column address;
--修改列的名称 alter table test modify address addresses varchar(40;
--修改列的属性 alter table test modi
create table test1( id number(9) primary key not null,
name varchar2(34) )
rename test2 to test;
--创建自增的序列 create sequence class_seq increment by 1 start with 1 MAXVALUE 999999 NOCYCLE NOCACHE;
select class_seq.currval from dual
--插入数据 insert into classes values(class_seq.nextval,'软件一班') commit;
--更新数据 update stu_account set username='aaa' where count_id=2; commit;
--创建唯一索引 create unique index username on stu_account(username); --唯一索引 不能插入相同的数据
--行锁 在新打开的对话中不能对此行进行操作 select * from stu_account t where t.count_id=2 for update; --行锁
--alter table stuinfo modify sty_id to stu_id;
alter table students drop constraint class_fk;
alter table students add constraint class_fk foreign key (class_id) references classes(id);
--外键约束 alter table stuinfo add constraint stu_fk foreign key (stu_id) references students(id) ON DELETE CASCADE;--外键约束,级联删除
alter table stuinfo drop constant stu_fk;
insert into students values(stu_seq.nextval,'张三',1,sysdate);
insert into stuinfo values(stu_seq.currval,'威海');
select * from stuinfo;
create table zhuce (zc_id number(9) not null primary key,
stu_id number(9) not null, zhucetime date default sysdate)
create table feiyong ( fy_id number(9) not null primary key,
stu_id number(9) not null, mx_id number(9) not null,
yijiao number(7,2) not null default 0,
qianfei number(7,2) not null )
create talbe fymingxi( mx_id number(9) not null primary key,
feiyong number(7,2) not null,
//共7位数字，小数后有两位
class_id number(9) not null }
create table card( card_id number(9) primary key,
stu_id number(9) not null,
money number(7,2) not null default 0,
status number(1) not null default 0 --0表可用,1表挂失 )
--链表查询
select c.classname||'_'||s.stu_name as 班级_姓名,si.address from classes c,students s , stuinfo si
where c.id=s.class_id and s.id=si.stu_id; insert into students values(stu_seq.nextval,'李四',1,sysdate);
insert into stuinfo values(stu_seq.currval,'南京');
--函数 select rownum,id,stu_name from students t order by id asc;
--中间表实现多对多关联 --（1 1， 1 n，n 1，n n ）
--1 n的描述 1的表不作处理 n的表有1表的字段 --1 1的描述 主外键关联 --n n的描述 中间表实现多对多关联
create table course( course_id number(9) not null,
couser_name varchar2(40) not null )
alter table course to couse;
create table stu_couse(stu_couse_id number(9) primary key,
stu_id number(9) not null, couse_id number(9) not null)
create unique index stu_couse_unq on stu_couse(stu_id,couse_id);
--唯一学生
create sequence stu_couse_seq increment by 1 start with 1 MAXVALUE 999999 NOCYCLE NOCACHE;
create sequence couses_seq increment by 1 start with 1 MAXVALUE 999999 NOCYCLE NOCACHE;
insert into course values(couses_seq.nextval,'计算机原理');
insert into course values(couses_seq.nextval,'编译原理');
insert into course values(couses_seq.nextval,'数据库原理');
insert into course values(couses_seq.nextval,'数据结构');
insert into course values(couses_seq.nextval,'计算机基础');
insert into course values(couses_seq.nextval,'C语言初步');
commit;
insert into stu_couse values(stu_couse_seq.nextval,1,1);
insert into stu_couse values(stu_couse_seq.nextval,1,3);
insert into stu_couse values(stu_couse_seq.nextval,1,5);
insert into stu_couse values(stu_couse_seq.nextval,1,5);
insert into stu_couse values(stu_couse_seq.nextval,2,1);
commit;
select * from stu_couse; select * from course;
--select s.stu_name,sc.couse_id, c.couser_name from students s,course c,stu_couse sc where stu_id=1
--select couse_id from stu_couse where stu_id=1
select cl.classname,s.stu_name,c.couser_name from stu_couse sc, students s,course c,classes cl where s.id=sc.stu_id and sc.couse_id=c.course_id and s.class_id=cl.id and s.id=1;
--班级——姓名
select c.classname,s.stu_name from students s,classes c where s.class_id=c.id and s.id=2;
select * from students s where s.id=2 --班级——姓名——课程
select cl.classname,s.stu_name,c.couse_name from stu_couse sc,students s,classes cl,couse c where sc.stu_id=s.id and sc.couse_id=c.couse_id and s.id=26;
--sql 语句的写法，现写出关联到的表，然后写出要查找的字段，第三 写出关联条件 ，记住在写关联到的表时先写数据多的表，这样有助于提高sql的效率
select c.couser_name,s.stu_name from stu_couse sc,students s,course c where c.course_id=1 and c.course_id=sc.couse_id and sc.stu_id=s.id;
select s.stu_name from students s,stu_couse sc where s.id=sc.stu_id group by s.id,s.stu_name;
select c.classname,count(sc.couse_id) from stu_couse sc,students s,classes c where s.class_id=c.id and s.id=sc.stu_id group by c.classname;
select s.stu_name, count(sc.couse_id) from stu_couse sc,students s,classes cl where s.id=sc.stu_id group by s.id,s.stu_name having count(sc.stu_couse_id)>3; 班级 学生 选课数量 select cl.classname,count(sc.stu_couse_id) from stu_couse sc,students s,classes cl where s.id=sc.stu_id and s.class_id=cl.id group by cl.classname;
--班级 学生 选课数量
select cl.classname,s.stu_name,count(sc.stu_couse_id) from stu_couse sc,students s,classes cl where s.id=sc.stu_id and s.class_id=cl.id group by s.stu_name;
select cl.classname,s.stu_name,count(sc.stu_couse_id) from stu_couse sc ,students s,classes cl where sc.stu_id=s.id and s.class_id=cl.id group by s.id;
select cl.classname,s.stu_name,count(sc.stu_couse_id) from stu_couse sc,students s,classes cl where sc.stu_id=s.id and s.class_id=cl.id group by s.stu_name; --班级 学生 所选课程id 所选课程名称
--创建试图 目的把表联合起来 然后看成一个表，在与其他的联合进行查询 create view xsxk as select cl.classname, s.stu_name,c.couse_id, c.couse_name from stu_couse sc,students s,classes cl,couse c where sc.stu_id=s.id and sc.couse_id=c.couse_id and s.class_id=cl.id;
select * from xsxk
create view classstu as select s.id,c.classname,s.stu_name from students s,classes c where c.id=s.class_id; drop view classstu;
--删除视图
select * from classstu;
create view stu_couse_view as select s.id ,c.couse_name from stu_couse sc,students s,couse c where s.id=sc.stu_id and sc.couse_id=c.couse_id;
select * from stu_couse_view;
create view csc as select cs.classname,cs.stu_name,scv.couse_name from classstu cs,stu_couse_view scv where cs.id=scv.id;
select * from csc;
select * from classes cross join students;
--全连接，相当于select * from classes,students;
select * from classes cl left join students s on cl.id=s.class_id;
--左连接 不管左表有没有 都显示出来 select * from classes cl right join students s on cl.id=s.class_id;
--右连接 select * from classes cl full join students s on cl.id=s.class_id;
--全连接
insert into classes values(class_seq.nextval,'软件四班');
create table sales( nian varchar2(4), yeji number(5) );
insert into sales values('2001',200); insert into sales values('2002',300);
insert into sales values('2003',400); insert into sales values('2004',500);
commit; select * from sales;
drop table sale;
