马士兵视频SQL代码

05 select
select ename||'daiosnad''dase' from emp;
select distinct deptno from emp; //去重复
select distinct deptno,job from emp; //重复的组合去掉


06 where
select * from emp where deptno = 10;//过滤条件
select * from emp where ename = 'CLARK';
select ename,sal from emp where sal >  1500;
select ename,sal,deptno from emp where deptno <>10;
select ename,sal from emp where ename > 'CBA';
select ename,sal from emp where sal between 800 and 1500;
select ename,sal from emp where sal >=800 and <=1500;
  空值处理
select ename,sal,comm from emp where comm is null; //选择comm为空值的
select ename,sal,comm from emp where comm is not null; //选择comm不为空值的
select ename,sal,comm from emp where sal in (800,1500,2000);//选择sal为800,1500,2000的
select ename,sal,comm from emp where ename in ('SMITH','KING');//选择ename为SIMTH,KING的
  简单日期处理
select ename,sal,hiredate from emp where hiredate > '20-2月-81';//简单日期处理
select ename,sal from emp where deptno = 10 and sal > 1000;
select ename,sal from emp where sal not in (800,1500);
  模糊查询
select ename from emp where ename like '%ALL%';   //%表示一个或者多个
select ename from emp where ename like '_A%';  //_表示一个字母
--select ename from emp where ename like '%\%%';  // 默认\为转义字符
--select ename from emp where ename like '%$%%' escape '$';  //指定$为转义字符


07 order by
select * from dept order by deptno desc; //desc 表示降序
select empno, ename from emp order by empno asc; //默认升序，或者asc
select empno, ename from emp where deptno <>10 order by empno asc; 
--select ename, sal, deptno from emp order by deptno asc, ename desc;


08 sql function_1
select lower(ename) from emp; //将ename全部变小写；
select ename from emp where lower(ename) like '_a%';
select substr(ename,1,3) from emp;//从第1个字符开始截，截3个字符
select chr(65) from dual;  //chr 将asc码转换为字符
select assii('A') from dual; //从字符获得ASC码
select round(23.23) from dual; // 取整
select round(23.231 , 1) from dual ;// 留1位小数
select to_char(sal, 'L99,999.9999') from emp;//将sal转换为99,999.9999的字符串形式  9代表一位数字
select to_char(sal, 'L00000.0000)from emp;// 9没有时不显示，0 强制显示
select to_char(hiredate, 'YYYY-MM-DD HH:MI:SS') from emp；  //显示时间
select to_char(sysdate, 'YYYY-MM-DD HH24:MI:SS') from dual;


09 sql function_2
select ename,hiredate from emp where hiredate > to_date('1981-2-20 12:34:56','YYYY-MM-DD HH24:MI:SS');  //to_date 将 字符串转换为日期
select sal from emp where sal > to_number('$1,250.00','$9,999.99');
select ename, sal*12 + nvl(comm, 0) from emp; // nvl如果comm中的值为空值，以0取代他


10 group gunction  //多输入 一输出


max min avg sum count


select max(sal) from emp; //取sal最大值
select min(sal) from emp;
select avg(sal) from emp;
select to_char(avg(sal),'99999999.99') from emp;
select round(avg(sal),2) from emp;
select sum(sal) from emp;
select count(*) from emp; //有多少条记录
select count(*) from emp where deptno =10;


select count(ename) from emp;
select count(comm) from emp;
select count(distinct deptno) from emp;


11 group by


select deptno,avg(sal) from emp group by deptno; //按deptno分组之后求均值
select deptno,job,max(sal) from emp group by deptno, job;//按两个字段deptno,job分组
select ename from emp where sal = (select max(sal) from emp);


12 having
select avg(sal),deptno from emp group by deptno having avg(sal) >2000;


select avg(sal) 
from emp 
where sal >1200
group by deptno
having avg(sal) > 1500
order by avg(sal) desc;


13 子查询
select ename, sal from emp
where sal > (select avg(sal) from emp);


select ename, sal from emp
join (select max(sal) max_sal, deptno from emp group by deptno) t
on (emp.sal = t.max_sal and emp.deptno = t.deptno);


14 self_table_connections


select e1.ename, e2.ename from emp e1 , emp e2 where e1.mgr = e2.empno;


15 1999sql


select ename,dname from emp join dept on (emp.deptno = dept.deptno);
select ename,grade from emp e join salgrade s on (e.sal between s.losal and  s.hisal);




三个表连接
select ename,dname,grade from
emp e join dept d on (e.deptno = d.deptno)
join salgrade s on (e.sal between s.losal and s.hisal)
where ename not like '_A%';


左外连接
select e1.ename, e2.ename from emp e1 left join emp e2 on (e1.mgr = e2.empno);
右外连接
select ename,dname from emp e right join dept d on (e.deptno = d.deptno);
全外连接
select ename,dname from emp e full join dept d on (e.deptno = d.deptno);




部门平均的薪水等级
select deptno,avg_sal,grade from
(select deptno, avg(sal) avg_sal from emp group by deptno) t
join salgrade s on (t.avg_sal between s.losal and s.hisal);


select deptno ,avg(sal) from
(select deptno ,sal, grade from emp join salgrade s on (emp.sal between s.losal and s.hisal)) t
group by deptno


--19_不用组函数 求薪水最大值
select distinct sal from emp where sal not in
(select distinct e1.sal from emp e1 join emp e2 on (e1.sal < e2.sal));




哪些人是经理人
select ename from emp where empno in (select mgr from emp);


20平均薪水最高部门的编号与名称
select dname,deptno from dept where deptno = (
select deptno from (select deptno,avg(sal) avg_sal from emp group by deptno)
where avg_sal = (select max(avg_sal) from (select deptno,avg(sal) avg_sal from emp group by deptno)))


select deptno,dept.dname from dept where dept.deptno = (
select deptno
from 
(select emp.deptno,avg(emp.sal) from emp group by deptno order by avg(sal) desc) 
where 
rownum =1)


select dname,deptno 
    from dept where deptno = (
        select deptno from 
(select deptno,avg(sal) avg_sal from emp group by deptno)
        where avg_sal = (select max(avg(sal)) from emp group by deptno))




22 平均薪水的等级最低的部门名称
select dname,t1.deptno,grade,avg_sal from (
       select deptno, grade,avg_sal from
                 (select deptno,avg(sal) avg_sal from emp group by deptno) t
                 join salgrade s on (t.avg_sal between s.losal and s.hisal)
       )t1
join dept on (t1.deptno = dept.deptno)
where t1.grade = (
  select min(grade) from (
       select deptno, grade,avg_sal from
                 (select deptno,avg(sal) avg_sal from emp group by deptno) t
                 join salgrade s on (t.avg_sal between s.losal and s.hisal)))
     


创建视图 --  v$dept_avg_sal_info
 create view v$dept_avg_sal_info as
select deptno, grade,avg_sal from
                 (select deptno,avg(sal) avg_sal from emp group by deptno) t
                 join salgrade s on (t.avg_sal between s.losal and s.hisal)




使用视图简化
select dname,t1.deptno,grade,avg_sal from 
      v$dept_avg_sal_info  t1
join dept on (t1.deptno = dept.deptno)
where t1.grade = (
  select min(grade) from (
       select deptno, grade,avg_sal from
                v$dept_avg_sal_info))




24_比普通员工薪水还要高的 经理人的名字
select ename from emp 
where empno in (select distinct mgr from emp where mgr is not null)
and sal >
(select max(sal) from emp
where empno not in (select distinct mgr from emp where mgr is not null))




25 rownum


复制备份表
create table emp2 as select * from emp;


26 update /transaction  事务
薪水翻倍
update emp2 set sal = sal*2 ,ename = ename||'-' where deptno = 10;


delete
delete from emp2 where deptno = 10;


commit 提交/ 修改起作用


27_create table 
create table  


create table stu 
  2  ( 
  3  id number(6),
  4  name varchar2(20) constraint stu_name_nn  not null,
  5  sex number(1),
  6  age number(3),
  7  sdate date,
  8  grade number(2) default 1,
  9  class number(4),
 10  email varchar2(50) unique  //字段级约束
 11  );




desc stu;




28_constraint  非空 唯一 主键 外键 cheak




名字和EMAIL的组合不重复
create table stu
  2  (
  3  id number(6),
  4  name varchar2(20) constraint stu_name_nn  not null,
  5  sex number(1),
  6  age number(3),
  7  sdate date,
  8  grade number(2) default 1,
  9  class number(4),
 10  email varchar2(50),
 11  constraint stu_name_email_uni unique(email,name) //表级约束
 12  );


主键约束  字段级约束
create table stu
  2  (
  3  id number(6) primary key, //主键 非空，唯一   代表了一条记录
  4  name varchar2(20) constraint stu_name_nn  not null,
  5  sex number(1),
  6  age number(3),
  7  sdate date,
  8  grade number(2) default 1,
  9  class number(4),
 10  email varchar2(50),
 11  constraint stu_name_email_uni unique(email,name) 
 12  );




主键约束  表级约束
create table stu
  2  (
  3  id number(6) , //主键 非空，唯一   代表了一条记录
  4  name varchar2(20) constraint stu_name_nn  not null,
  5  sex number(1),
  6  age number(3),
  7  sdate date,
  8  grade number(2) default 1,
  9  class number(4) ,
 10  email varchar2(50),
 11  constraint stu_name_email_uni unique(email,name) ,
 12  constraint stu_id_pk primary key (id)
 13  );






外键  字段级约束
create table stu
  2  (
  3  id number(6) , //主键 非空，唯一   代表了一条记录
  4  name varchar2(20) constraint stu_name_nn  not null,
  5  sex number(1),
  6  age number(3),
  7  sdate date,
  8  grade number(2) default 1,
  9  class number(4) references class(id),
 10  email varchar2(50),
 11  constraint stu_name_email_uni unique(email,name) ,
 12  constraint stu_id_pk primary key (id)
 13  );


外键  表级约束  被参考的字段 必须是主键
create table stu
  2  (
  3  id number(6) , //主键 非空，唯一   代表了一条记录
  4  name varchar2(20) constraint stu_name_nn  not null,
  5  sex number(1),
  6  age number(3),
  7  sdate date,
  8  grade number(2) default 1,
  9  class number(4) ,
 10  email varchar2(50),
 11  constraint stu_class_fk foreign key(class) references class(id),
 12  constraint stu_name_email_uni unique(email,name) ,
 13  constraint stu_id_pk primary key (id)
 14  );


create table calss
(
id number(4) primary key,
name varchar2(20) not null
)


31_alter
修改表结构


alter table stu add(addr varchar2(100));// 增加字段
alter table stu drop(addr);//删减字段
alter table stu modify(addr varchar2(150));//修改字段 修改后要能容纳原来的数据
alter table stu drop constraint sut_clall_fk;//删除约束条件
alter table stu add constraint stu_class_fk foreign key (class) references class(id);//增加约束条件