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)
);
-----------------------------------------------------------------------------------------------------------
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
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