--查找emp表
select * from emp;
--查找emp表的sal
select a.SAL from emp a;
--查找emp表的ename
select a.ename from emp a;
--emp表的sal*10
select a.SAL*10 from emp a;
--emp表的sal的平均值
select avg(a.sal) from emp a;
--emp表的sal的总和
select sum(a.sal) from emp a;
--emp表的sal的max
select max(a.sal) from emp a;
--emp表的sal的min
select min(a.sal) from emp a;
--emp表中sal<1000的信息
select * from emp where sal<1000;
--ename中含有A的信息
select ename from emp where ename like'%A%';
--emp中ename不含有A的信息
select * from emp where ename not like'%A%';
--查询系统时间
select sysdate from dual;
--计算薪资小于5000的员工的工资总和
select sum(sal) from emp where sal<5000 ;
--计算工资不高于平均工资的工资总和
select sum(sal) from emp where sal<(select avg(sal) from emp);
--计算工资小于4000的员工的平均工资
select avg((select sum(sal) from emp where sal<4000)) from emp;
--查询薪水低于100000的员工姓名和sal
select ename,sal from emp where sal<100000;
--计算20号部门的员工的最高工资和最低工资
select max(sal),min(sal) from emp where deptno=20;
--查询工资大于1000，并且是20号部门的员工的全部信息
select * from emp where sal>1000 and deptno=20;
--求最高工资的员工的员工姓名和部门名称
select ename,deptno,sal from emp where sal=(select max(sal) from emp);
--将员工薪水小于5000且部门平均薪水大于1000的部门标号列出，按部门平均薪水降序排序
select deptno from emp where sal<5000 group by deptno having avg(sal) >1000;
select sal from emp order by sal desc;
Order by *** desc
--查找表emp
select * from emp ;
--根据用户名“Smiths”查找他所在的部门
select deptno from emp where ename='SMITH';
--查询每个部门的最高工资的人员名称
select e.ename,e.deptno,e.sal from (select deptno as did ,max(sal) as m from emp group by deptno ) s,emp e,dept d where e.sal=s.m and s.did=e.deptno and d.deptno=e.deptno;
--查询“Jones”之后第一个进入公司的人
select * from emp where hiredate=(select min(hiredate) from emp where hiredate>(select hiredate from emp where ename='JONES')) ;
--5.查找工资最高的部门名称和工资最低的部门名称及工资
select d.dname,e.sal from emp e,dept d where e.deptno=d.deptno and sal=(select max(m) from (select deptno,max(sal) as m from emp e group by deptno) s)
union
select d.dname,e.sal from emp e,dept d where e.deptno=d.deptno and sal=(select min(m) from (select deptno,min(sal) as m from emp e group by deptno) s)
--创建表
create table student(
StudentId number (6),--学号
LoginPwd varchar(20),--密码
StudentName varchar(50),--姓名
Sex char(2),--性别
Gradeld Number(6),--所在年级
Phone number(15),--联系电话
Address varchar2(255),--现住址
BornDate Date,--出生日期
Emile varchar2(50)--电子邮件
);
--添加数据
insert into student values(1001,'123456','赵六','男',1507,120,'北京','23-5月-1995','@10422');
insert into student values(1002,'123456','王五','女',1507,110,'北京','23-5月-1995','@10422');
insert into student values(1003,'123456','张三','男',1507,120,'北京','23-5月-1995','@10422');
insert into student values(1004,'123456','李四','女',1507,110,'北京','23-5月-1995','@10422');
--提交
commit;
--查询此表
select * from student;
--根据条件修改
update student set studentname='孙七',loginpwd='666666' where studentid=1001;
select * from student;
--根据条件删除
delete from student where studentid=1002;
select * from student;
--增加字段
ALTER TABLE 表名称 ADD(列名称 数据类型 [DEFAULT 默认值],列名称 数据类型 [DEFAULT 默认值],…)
--删除此表
drop table student;
--B卷 创建表空间
create tablespace mytestspace datafile 'e:week3.dbf' size 2M;
--创建用户
create user zhangsan identified by zhangsan default tablespace mytestspace
temporary tablespace temp;
--创建角色并授权
create role fang;
grant create table to fang;
grant fang to zhangsan;
grant dba to zhangsan;
--创建表
create table teacher (
tid number primary key,
tname varchar2(50),
tdate date,
address varchar2(100)
);
select * from teacher;
--创建序列
create sequence teachers_sequence minvalue 1 maxvalue 100 (最小值，最大值)cycle (循环)increment by 1(步长值) start with 1（从1开始）;
insert into teacher values(teachers_sequence.nextval,'小李','01-1月-1999','北京');
insert into teacher values(teachers_sequence.nextval,'小张',to_date('1982-1-1','yyyy-mm-dd'),'北京');