oracle——笔记——DDL语句

create table emp2 ( empno number(4),
                    ename varchar2(10),
                    job varchar2(9),
                    mgr number(4),
                    hiredate date,
                    sal number(7,2),
                    comm number(7,2),
                    deptno number(2) 
                 );
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insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7369, 'SMITH', 'CLERK', 7902, to_date('17-12-1980', 'dd-mm-yyyy'), 800.00, null, 20);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7499, 'ALLEN', 'SALESMAN', 7698, to_date('20-02-1981', 'dd-mm-yyyy'), 1600.00, 300.00, 30);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7521, 'WARD', 'SALESMAN', 7698, to_date('22-02-1981', 'dd-mm-yyyy'), 1250.00, 500.00, 30);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7566, 'JONES', 'MANAGER', 7839, to_date('02-04-1981', 'dd-mm-yyyy'), 2975.00, null, 20);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7654, 'MARTIN', 'SALESMAN', 7698, to_date('28-09-1981', 'dd-mm-yyyy'), 1250.00, 1400.00, 30);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7698, 'BLAKE', 'MANAGER', 7839, to_date('01-05-1981', 'dd-mm-yyyy'), 2850.00, null, 30);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7782, 'CLARK', 'MANAGER', 7839, to_date('09-06-1981', 'dd-mm-yyyy'), 2450.00, null, 10);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7788, 'SCOTT', 'ANALYST', 7566, to_date('19-04-1987', 'dd-mm-yyyy'), 3000.00, null, 20);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7839, 'KING', 'PRESIDENT', null, to_date('17-11-1981', 'dd-mm-yyyy'), 5000.00, null, 10);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7844, 'TURNER', 'SALESMAN', 7698, to_date('08-09-1981', 'dd-mm-yyyy'), 1500.00, 0.00, 30);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7876, 'ADAMS', 'CLERK', 7788, to_date('23-05-1987', 'dd-mm-yyyy'), 1100.00, null, 20);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7900, 'JAMES', 'CLERK', 7698, to_date('03-12-1981', 'dd-mm-yyyy'), 950.00, null, 30);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7902, 'FORD', 'ANALYST', 7566, to_date('03-12-1981', 'dd-mm-yyyy'), 3000.00, null, 20);

insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7934, 'MILLER', 'CLERK', 7782, to_date('23-01-1982', 'dd-mm-yyyy'), 1300.00, null, 10);

=============================================================================================================================

create table dept2 ( deptno number(2),
                     dname varchar2(14),
                     loc varchar2(13)
                   );

----------------------------------------------------

insert into dept2 (DEPTNO, DNAME, LOC)
values (10, 'ACCOUNTING', 'NEW YORK');

insert into dept2 (DEPTNO, DNAME, LOC)
values (20, 'RESEARCH', 'DALLAS');

insert into dept2 (DEPTNO, DNAME, LOC)
values (30, 'SALES', 'CHICAGO');

insert into dept2 (DEPTNO, DNAME, LOC)
values (40, 'OPERATIONS', 'BOSTON');

============================================================

create table salgrade2 ( grade number,
                         losal number,
                         hisal number
                       );

--------------------------------------------------

insert into salgrade2 (GRADE, LOSAL, HISAL)
values (1, 700, 1200);

insert into salgrade2 (GRADE, LOSAL, HISAL)
values (2, 1201, 1400);

insert into salgrade2 (GRADE, LOSAL, HISAL)
values (3, 1401, 2000);

insert into salgrade2 (GRADE, LOSAL, HISAL)
values (4, 2001, 3000);

insert into salgrade2 (GRADE, LOSAL, HISAL)
values (5, 3001, 9999);


========================================================

select * from emp2;

select * from dept2;

select * from salgrade2;

=====================================
select * from emp2;        --employee2 员工表
select * from dept2;       --department2 部门表
select * from salgrade2;   -- salary grade2 工资等级表

-----------------------------------------------------
emp2

empno    员工编号
ename    员工姓名
job      工作/工种
mgr      manager上级编号
hiredate 入职日期
sal      salary 工资
comm     奖金/津贴
deptno   部门编号
---------------------

dept2

deptno  部门号
dname   部门名称
loc     所在地
---------------------------
salgrade2

grade                   等级
losal lowest salary     最低工资
hisal high salary       最高工资

=============================================


 
DDL语句:


create 创建表:

默认值
  create table emp94(eid number(4) default 1234,
                     ename varchar2(10) default 'abc',
                     birth date default to_date('2007-7-1','YYYY-MM-DD')
                    );
                     
  insert into emp94(eid) values(1122);
  
  insert into emp94 values(1122,null,null);
  
  
  




  
复制表 CTAS:


  create table 表名 as 子查询语句;
  
  create table db_emp2 as select * from emp;
  
  create table demp as select * 
                       from emp e join dept d 
                       on e.deptno = d.deptno;
                       
      





                 
                       
alter 修改表:

  alter table emp94 add addr varchar2(40);               --新增列
  
  alter table emp94 add addr varchar2(40) default 'ZZZ'; --同时设置默认值
  
  alter table emp94 modify addr char(10);                --修改列 类型和长度
  
  alter table emp94 modify birth default sysdate;         --修改列 默认值
  
  alter table emp94 modify eid default null;              --清除默认值
  
  alter table emp94 rename column birth to birthday;      --修改列名
  
  alter table emp_94 drop column birthday;                --删除列
  
  rename emp94 to emp_94;                                 ---修改表名
  
  select * from emp_94;
  







drop 删除表:


 drop table 表名;
 
 drop table db_emp;
 







truncate 截断表:


 truncate table 表名;
 
 truncate table db_emp;     --delete from db_emp
 
 select * from db_emp;
 
 






 比较drop、truncate、delete
 
 1）drop和truncate属于DDL语句，执行结果自动提交/保存；
 
    delete属于DML语句，执行之后需要手动提交；在commit之前可以rollback;
    
 2）drop删除表中数据，同时删除表;
 
    truncate和delete只删除表中的数据;
    
 3）truncate只能删除整张表的数据；
 
    delete可以删除整张表的数据，也可以删除where条件指定的数据;
    
 4）执行速度：drop > truncate > delete;
 
 5）drop和truncate释放存储空间，delete不释放;
    








约束:


1）主键约束  primary key，唯一性和非空性

2）唯一约束  unique，     值唯一，但是可以为空

3）非空约束  not null，   值非空，但是可以重复

4）检查约束  check，      规定列的取值范围/值域

                  check(sal between 6000 and 10000)
                  check(sex in('男','女','不详'))
                  
5）外键约束  foreign key，表与表之间的关系

select * from emp;

select * from dept;


insert into emp(empno,deptno) values(4972,50);

insert into dept(deptno) values(50);

delete from dept where deptno = 50;




创建表的同时创建约束:


 create table db_emp(sid number(4),
                     sname varchar2(10) not null,
                     age number(3),
                     addr varchar2(40),
                     parents varchar(10),
                     classno number(2),
                     constraints pk_db_emp primary key(sid),
                     constraints uk_db_emp unique(addr),
                     constraints ck_db_emp check(age between 12 and 18),
                     constraints fk_db_emp foreign key(classno) 
                                           references dept(deptno)
                      );
                      
 insert into db_emp values(14,'XX',18,'NanJing',null,10)    
                 
 select * from db_emp2; 
 
 delete from db_emp where sid = 13;
 
 




表已经存在，创建/删除、约束失效/生效:


 alter table db_emp drop constraints UK_DB_EMP;
 
 alter table db_emp add constraints uk_db_emp unique(addr);
 
     ---主键 外键 唯一 检查约束

 alter table db_emp modify sname null;
 
 alter table db_emp modify parents not null;
 
 alter table db_emp enable constraints UK_DB_EMP;  --生效
 
 alter table db_emp disable constraints UK_DB_EMP; --失效