Oracle创建表管理表

 --创建图书表
 create table books_lib
 (
  book_id number(10) primary key,  --unique&not null
  book_name varchar2(50) not null
 );
 alter table books_lib add publisher  varchar2(50) null;
 desc books_lib;
 --增加check约束
 alter table books_lib  add qty number check(qty>0 and qty<100) unique  not null ;
 insert into books_lib values (1,'Oracle编程','中国出版公司',1000);
 to_date('1998-07-05','yyyy-mm-dd');
 --
 create table emp_virtual(
    empno varchar2(10) primary key,
    sal number(7,2),
    comm_rct number(7,2),
    comm_sal number(7,2) generated always as (sal*comm_rct) virtual
 );
 insert into emp_virtual(empno,sal,comm_rct) values ('BN7369',5000,0.23);
 select * from emp_virtual;
 update emp set sal=5000 where empno=7369;
 delete * from emp_virtual
 --修改表列
 alter table books_lib modify publisher varchar2(100);
 --删除默认值
 alter table  books_lib modify publish_date default null;
 --删除表列
 alter table books_lib drop column publish_date;
 --同时删除publisher和qty列，并删除与其相关的多列约束
 alter table books_lib drop (publisher,qty) cascade constraint;
 --部分删除表列
 删除大量的数据，需要执行很长的时间
 将drop column替换成set unused  未使用状态
 alter table boos_lib set unused(isbn)  cascade constraint;
 --删除被标记为unused的列
 alter table books_lib drop unused columns;
 --重命名表列
 alter table books_lib rename column qty to books_qty;
 --重命名表
 alter table scott.bookslib rename to booksnewlib;
 --删除数据表
 drop table  books_lib;
 --从回收站（闪回恢复区）中恢复表
 flashback table books_lib to before drop;
 --立即删除，无法恢复
 drop table books_lib cascade constraints purge;

 --表注释
 comment on table student is '学生表'；
 comment on column student.sno is '学号（主键）';
 --查看表的comment
 select  * from  all_tab_comments where table_name=upper('student');
 --查看列的comment
 select * from  all_col_comments where  table_name=upper('student');

 CREATE TABLE STUNDET
 (
 CONSTRAINT FK_BLUE  FOREIGN KEY(ID) REFRENCES CLASSid(id)
 )

 外键约束的作用
        外键是该表是另一个表之间联接的字段 外键必须为另一个表中的主键 外键的用途是确保数据的完整性。它通常包括以下几种： 实体完整性，确保每个实体是唯一的（通过主键来实施） 

 1 域完整性，确保属性值只从一套特定可选的集合里选择
 2 关联完整性，确保每个外键或是NULL（如果允许的话）或含有与相关主键值相配的值    

 有外键约束的表CRUD操作
   1   增加数据：先插入外表，再插入主表
   2   删除数据：先删除主表再删除外表，
   3   有对应记录的值，不能修改当前列；

 create table teacher(
        tno   varchar2(3) not null,
        tname varchar2(9) not null,
        tsex  varchar2(3) not null,
        tbirthday date,
        prof  varchar2(9),
        depart varchar2(15) not null,
        constraint pk_teacher primary key(tno)
 );

 create table course(
        cno       varchar2(5) not null,
        cname     varchar2(15) not null,
        tno       varchar2(3) not null,
        constraint pk_course primary key(cno)
 );
 create table student(
        sno   varchar2(3) not null,
        sname varchar2(9) not null,
        ssex  varchar2(3) not null,
        sbirthday date,
        sclass varchar2(5),
        constraint pk_student primary key(sno)
 );
 comment on column student.sno is '学号（主键）';
 create table score(
         sno   varchar2(3) not null,
         cno   varchar2(5) not null,
         degree   number(4,1),
         constraint pk_score primary key(sno,cno)--复合主键
 );
 comment on column score.sno is '学号（主键）';

 alter table score add constraint fk_sno foreign key(sno) references student(sno);
 --Student表
 insert into student(sno,sname,ssex,sbirthday,sclass) values(108,'曾华','男',to_date('1977-09-01','yyyy-mm-dd'),95033);
 --score表（添加外键后要先填Student，course表中数据去满足外键约束）
 insert into course(cno,cname,tno) values('3-105','计算机导论',825);

 --添加外键
 alter table course add constraint fk_tno foreign key(tno) references teacher(tno);
 alter table emp add  constraint  fk_deptno foregin key(deptno) references dept(deptno);

 已存在数据,如何修改表类型
 --修改表名，表列
 create table test( name1 varchar2(10), email varchar2(10));
 alter table test1  add email varchar2(20)
 alter table test1 drop column email
 alter table test rename to test1   --修改表名
 alter table  test1 rename column name1 to name --修改列名
 alter table  test1 modify name varchar2(10);  --修改字段类型
 --1 修改原字段名
 alter table test1 rename column name  to name1;
 --2 增加一个与原字段同名字段
 alter table test1  add name varchar2(10);
 --3 将原字段的数据增加到新的字段
 update test1 set name=trim(name1);
 --4 更新完删除字段
 alter table test1  drop column name1;

 学生系统建表
 --建表
 --student表+注释
 create table student(
 sno varchar2(3) not null,
 sname varchar2(9) not null,
 ssex varchar2(3) not null,
 sbirthday date,
 sclass varchar2(5),
 constraint pk_student primary key(sno)
 );
 comment on column student.sno is '学号（主键）';
 comment on column student.sname is '学生姓名';
 comment on column student.ssex is '学生性别';
 comment on column student.sbirthday is '学生出生年月日';
 comment on column student.sclass is '学生所在班级';
 --course表+注释
 create table course(
 cno varchar2(5) not null,
 cname varchar2(15) not null,
 tno varchar2(3) not null,
 constraint pk_course primary key(cno)
 );
 comment on column course.cno is '课程编号（主键）';
 comment on column course.cname is '课程名称';
 comment on column course.tno is '教工编号（外键）';
 --score表+注释
 create table score(
 sno varchar2(3) not null,
 cno varchar2(5) not null,
 degree number(4,1),
 constraint pk_score primary key(sno,cno)
 );
 comment on column score.sno is '学号（主键）';
 comment on column score.cno is '课程编号（主键）';
 comment on column score.degree is '成绩';
 --teacher表+注释
 create table teacher(
 tno varchar2(3) not null,
 tname varchar2(9) not null,
 tsex varchar2(3) not null,
 tbirthday date,
 prof varchar2(9),
 depart varchar2(15) not null,
 constraint pk_teacher primary key(tno)
 );
 comment on column teacher.tno is '教工编号（主键）';
 comment on column teacher.tname is '教工姓名';
 comment on column teacher.tsex is '教工性别';
 comment on column teacher.tbirthday is '教工出生年月';
 comment on column teacher.prof is '职称';
 comment on column teacher.depart is '教工所在单位';
 --添加外键
 alter table course add constraint fk_tno foreign key(tno) references teacher(tno);
 alter table score add constraint fk_sno foreign key(sno) references student(sno);
 alter table score add constraint fk_cno foreign key(cno) references course(cno);
 --添加数据
 --Student表
 insert into student(sno,sname,ssex,sbirthday,sclass) values(108,'曾华','男',to_date('1977-09-01','yyyy-mm-dd'),95033);
 insert into student(sno,sname,ssex,sbirthday,sclass) values(105,'匡明','男',to_date('1975-10-02','yyyy-mm-dd'),95031);
 insert into student(sno,sname,ssex,sbirthday,sclass) values(107,'王丽','女',to_date('1976-01-23','yyyy-mm-dd'),95033);
 insert into student(sno,sname,ssex,sbirthday,sclass) values(101,'李军','男',to_date('1976-02-20','yyyy-mm-dd'),95033);
 insert into student(sno,sname,ssex,sbirthday,sclass) values(109,'王芳','女',to_date('1975-02-10','yyyy-mm-dd'),95031);
 insert into student(sno,sname,ssex,sbirthday,sclass) values(103,'陆君','男',to_date('1974-06-03','yyyy-mm-dd'),95031);
 insert into student(sno,sname,ssex,sbirthday,sclass) values(104,'周晶晶','女',to_date('1974-06-03','yyyy-mm-dd'),95031);
 --teacher表
 insert into teacher(tno,tname,tsex,tbirthday,prof,depart) values(804,'李诚','男',to_date('1958/12/02','yyyy-mm-dd'),'副教授','计算机系');
 insert into teacher(tno,tname,tsex,tbirthday,prof,depart) values(856,'张旭','男',to_date('1969/03/12','yyyy-mm-dd'),'讲师','电子工程系');
 insert into teacher(tno,tname,tsex,tbirthday,prof,depart) values(825,'王萍','女',to_date('1972/05/05','yyyy-mm-dd'),'助教','计算机系');
 insert into teacher(tno,tname,tsex,tbirthday,prof,depart) values(831,'刘冰','女',to_date('1977/08/14','yyyy-mm-dd'),'助教','电子工程系');
 --course表(添加外键后要先填teacher表中数据去满足外键约束)
 insert into course(cno,cname,tno) values('3-105','计算机导论',825);
 insert into course(cno,cname,tno) values('3-245','操作系统',804);
 insert into course(cno,cname,tno) values('6-166','数字电路',856);
 insert into course(cno,cname,tno) values('9-888','高等数学',831);
 --score表（添加外键后要先填Student，course表中数据去满足外键约束）
 insert into score(sno,cno,degree) values(103,'3-245',86);
 insert into score(sno,cno,degree) values(105,'3-245',75);
 insert into score(sno,cno,degree) values(109,'3-245',68);
 insert into score(sno,cno,degree) values(103,'3-105',92);
 insert into score(sno,cno,degree) values(105,'3-105',88);
 insert into score(sno,cno,degree) values(109,'3-105',76);
 insert into score(sno,cno,degree) values(101,'3-105',64);
 insert into score(sno,cno,degree) values(107,'3-105',91);
 insert into score(sno,cno,degree) values(108,'3-105',78);
 insert into score(sno,cno,degree) values(101,'6-166',85);
 insert into score(sno,cno,degree) values(107,'6-166',79);
 insert into score(sno,cno,degree) values(108,'6-166',81);

 --创建scott方案下的emp表副本并包含所有数据
 create table emp_copy as select * from emp;
 --创建一个架构而不包含任何表数据
 create table emp_copy as select * from emp where 1=0;
    select * from emp_copy;
 --通过改变select 语句,创建不完全相同的类型
 create table emp_copy_others as select empno,
 to_char(hiredate,'yyyy-MM-dd') as hiredate from emp;

 -- 在约束中使用函数和布尔
 create table invoice_check_others
 (
  invoice_name varchar2(20),
  invoice_type int,
  invoice_total number(9,2) default 0,
  constraint invoice_ck CHECK(invoice_total between 1 and 1000),
  constraint check_invoice_type check(invoice_type in(1,2,3,4)),
  constraint check_invoice_name check(invoice_name=upper(invoice_name))--必须大写
 )    

 --查看表中所有的约束
 select constraint_name,search_condition,status from user_constraints
 where table_name=upper('invoice_check_others');

 --Merge语句
 create table dept60_bonuses
 (
 empno number,bonus_amt number
 );
 insert into dept60_bonuses values(7369,0);
 insert into dept60_bonuses values(7788,2);
 insert into dept60_bonuses values(7876,3);
 select  empno,sal,ename from emp
 select * from dept60_bonuses
 --合并两张表,根据不同的语句删除,更新
 --合并两张表,根据不同的语句删除,更新
 merge into dept60_bonuses b
 using ( select empno,sal,deptno from emp where deptno=20) e
 on (b.empno=e.empno)
 when matched then
 update set b.bonus_amt =e.sal*0.2
 where b.bonus_amt=0
 delete where (e.sal>2500)
 when not matched then
 insert (b.empno,b.bonus_amt)
 values (e.empno,e.sal*0.1)
 where (e.sal<4000);