select userenv('language') from dual;--AMERICAN_AMERICA.ZHS16GBK
select * from V$NLS_PARAMETERS--AMERICAN
--===========解锁scott用户并重新设置密码
alter user scott account unlock;
alter user scott identified by tiger;
--===========基本查询
--1.查询出所有emp中的信息,并用中文进行字段重命名
select empno as "员工编号",ename "员工姓名",job 工作,mgr "上级领导",hiredate "入职日期",sal "工资",comm "奖金",deptno "部门编号" from emp;
--2.查询emp表中员工的job信息,并去除重复信息
select distinct(job) from emp;
--3.查询emp表中员工的全年的工资总和(sal总和)
select ename,sal* 12 from emp;
--4.查询emp表中员工的全年收入总和(sal+comm的总和)
select ename,sal*12 + nvl(comm,0) from emp;
--5.查询emp表中员工编号,姓名
--输出格式如下:编号:xxx,姓名:xxx
----Concat拼接方式
select concat('编号:',empno) from emp;
select concat(concat('编号:',empno),concat(',姓名:',ename)) from emp;
----Oracle的||方式
select '编号:'||empno||',姓名:'||ename from emp;
--=============================================条件查询
--1.查询工资大于1500的员工
select * from emp where sal > 1500;
--2.查询工资大于1500并且有奖金的雇员
select * from emp where sal > 1500 and comm is not null;
--3.查询工资大于1500或者有奖金的雇员
select * from emp where sal > 1500 or comm is not null;
--4.查询工资大于1500并且没有奖金的雇员
select * from emp where sal > 1500 and comm is null;
--5.查询员工姓名为smith的员工
select * from emp where ename = 'SMITH';
--=============================================范围查询
--1.查询工资大于1500但小于3000的全部雇员
---->=,<=方式
select * from emp where sal >=1500 and sal <= 3000;
----between and方式
select * from emp where sal between 1500 and 3000;
--2.查询1981-1-1到1981-12-31号入职的雇员(between and)
select * from emp where hiredate between to_date('1981-1-1','yyyy-MM-dd') and to_date('1981-12-31','yyyy-MM-dd')
--3.查询员工编号是7369,7654,7566的员工
----OR方式
select * from emp where empno = 7369 or empno = 7654 or empno = 7566;
----IN方式
select * from emp where empno in (7369,7654,7566);
--4.查询雇员姓名是'SMITH','ALLEN','WARD'的雇员信息
----IN方式
select * from emp where ename in ('SMITH','ALLEN','WARD');
--=============================================模糊查询like
--1.查询所有雇员姓名中第二个字符有‘M’的雇员
select * from emp where ename like '_M%';
--2.查询名字中带有‘M’的雇员
select * from emp where ename like '%M%';
--3.查询雇员编号不是7369的雇员信息
----<>方式
select * from emp where empno <> 7369;
----!=方式
select * from emp where empno != 7369;
--=============================================排序 order by
--1.查询雇员的工资进行降序排序
select * from emp order by sal desc;
--2.查询雇员的奖金并做降序排序(关于nulls first/nulls last)
select * from emp order by comm desc nulls last;
--3.查询雇员的工资做降序排列并且其中奖金部分是升序排序
select * from emp order by sal desc,comm asc;
--===========单行函数
--字符函数
--1.将'smith'转换成大写--关键字:upper
select upper('smith') from dual;
--2.将'SMITH'转换成小写--关键字:lower
select lower(ename) from emp;
--3.将'smith'首字母大写--关键字:initcap
select initcap('smith') from dual;
--4.将'helloworld'截取字符串成'hello'--关键字substr
select substr('helloworld',0,5) from dual;
--5.获取'hello'的字符串长度--关键字length
select length('hello' ) from dual;
--6.将'hello'中的l用x进行替换--关键字replace
select replace('hello','l','x') from dual;
--数值函数
--1.将15.66进行四舍五入(从-2到2)--关键字round
select round(15.66) from dual; --16
select round(15.66,-2) from dual;--0
select round(15.66,-1) from dual;--20
select round(15.66,0) from dual; --16
select round(15.66,1) from dual; --15.7
select round(15.66,2) from dual; --15.66
--2.将15.66进行截断(从-2到2)--关键字trunc
select trunc(15.66) from dual;
select trunc(15.66,-2) from dual; --0
select trunc(15.66,-1) from dual; --10
select trunc(15.66,0) from dual; --15
select trunc(15.66,1) from dual; --15.6
select trunc(15.66,2) from dual; --15.66
--3.对15/3进行求余数--关键字mod
select mod(15,3) from dual;
--日期函数
--1.查询系统时间--关键字sysdate
select sysdate from dual;
--2.查询雇员进入公司的周数
select ename,(sysdate-hiredate)/7 from emp;
--3.查询雇员进入公司的月数--关键字months_between
select ename,months_between(sysdate,hiredate) from emp;
--4.求出三个月后的日期--关键字add_months
select ename,add_months(hiredate,3) from emp;
--转换函数
--1.将系统日期显示为yyyy-mm-dd hh:mi:ss(去掉补零和24小时显示时间)--关键字to_char
select to_char(sysdate,'yyyyfm-mm-dd hh24:mi:ss') from dual;
----显示成年月日
select to_char(sysdate,'yyyyfm-mm-dd hh24:mi:ss') from dual;
select to_char(sysdate,'yyyy')||'年'||to_char(sysdate,'MM')||'月' from dual;
--2.将字符串'1981-1-1'转换成日期类型--关键字to_date
select to_date('1981-1-1','yyyy-MM-dd') from dual;
select to_number('99.') from dual;
select to_char(99) from dual;
--通用函数
--1.空值的处理函数
select nvl(comm,0) from emp;
--2.nvl2(判断值,空返回值,非空返回值)
select nvl2(3,'1','2') from dual;
192.168.124.29/
--条件表达式
--1.查询员工的job内容并转成中文显示
----decode方式
select ename,decode(job,'CLERK','柜员','SALESMAN','销售','MANAGER','管理','其他') from emp;
----case when then end方式
select ename,case job
when 'CLERK' then '柜员'
when 'SALESMAN' then '销售'
when 'MANAGER' then '管理'
else
'其他'
end from emp;
--===========多行函数
--1.查询所有员工记录数--关键字count
select count(empno) from emp;
--2.查询佣金的总数--(如何查询某个字段的总数量)
select sum(sal) from emp;
--3.查询最低工资--关键字min
select min(sal) from emp;
--4.查询最高工资--关键字max
select max(sal) from emp;
--5.查询平均工资--关键字avg
select avg(sal) from emp;
--6.查询20号部门的员工工资总和
select sum(sal) from emp where deptno = 20;
--======================================分组函数
--1.查询部门编号及人数--分组查询关键字group by
select deptno,count(*) from emp group by deptno;
--2.查询每个部门编号及平均工资
select deptno,avg(sal) from emp group by deptno;
--3.查询部门名称,部门编号,平均工资
select dname,emp.deptno,avg(sal) from emp,dept where emp.deptno = dept.deptno group by dname,emp.deptno;
--4.查询出部门人数大于5人的部门
select deptno,count(*) from emp group by deptno having count(*)>5 ;
--5.查询部门编号,部门名称,平均工资且平均工资大于2000
select emp.deptno,dname,avg(sal) from emp,dept where emp.deptno = dept.deptno
group by emp.deptno,dname
having avg(sal) > 2000;
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--======================================多表关联查询
--查询员工编号,员工姓名,员工部门编号,员工部门名称,员工部门地址,中文显示员工工资等级,
--及领导编号,领导姓名,领导部门编号,领导部门名称,中文显示领导工资等级
select e1.empno,e1.ename,e1.deptno,d1.dname,d1.loc,decode(s1.grade,1,'一级',2,'二级',3,'三级',4,'四级',5,'五级','其他') as sallevel,e2.empno,
e2.ename,e2.deptno,d2.dname,d2.loc,decode(s2.grade,1,'一级',2,'二级',3,'三级',4,'四级',5,'五级','其他') as sallevel from emp e1,dept d1,salgrade s1,emp e2,dept d2,salgrade s2
where e1.mgr = e2.empno and e1.deptno = d1.deptno and e1.sal between s1.losal and s1.hisal
and e2.deptno = d2.deptno and e2.sal between s2.losal and s2.hisal;
select * from emp;
select * from salgrade;
select * from dept;
--1.查询员工编号,员工姓名,领导编号,领导姓名
--2.查询员工编号,员工姓名,员工部门编号,员工部门名称,员工部门地址,领导编号,领导姓名,领导部门编号,领导部门名称
--3.查询员工编号,员工姓名,员工部门编号,员工部门名称,员工部门地址,员工工资等级,领导编号,领导姓名,领导部门编号,领导部门名称,领导工资等级
--4.查询员工编号,员工姓名,员工部门编号,员工部门名称,员工部门地址,中文显示员工工资等级,领导编号,领导姓名,领导部门编号,领导部门名称,中文显示领导工资等级
select e1.empno,e1.ename,e1.deptno,d1.dname,d1.loc,
decode(s1.grade,1,'一级',2,'二级',3,'三级',4,'四级',5,'五级','其他') as sallevel,
e2.empno,e2.ename,e2.deptno,d2.dname,
decode(s2.grade,1,'一级',2,'二级',3,'三级',4,'四级',5,'五级','其他') as sallevel
from emp e1,salgrade s1,dept d1,dept d2,salgrade s2,emp e2
where e1.mgr = e2.empno and d1.deptno = e1.deptno and e1.sal
between s1.losal and s1.hisal and e2.sal between s2.losal and s2.hisal
and d2.deptno = e2.deptno
--======================================外连接
--1.查询员工编号,姓名,领导编号,领导姓名,包括没领导的
----left join on方式
select e1.empno,e1.ename,e2.empno,e2.ename from emp e1 left join emp e2 on e1.mgr = e2.empno;
----Orcl的(+)方式
select e1.empno,e1.ename,e2.empno,e2.ename from emp e1,emp e2 where e1.mgr = e2.empno(+);
--2.查询出所有部门信息(包括没员工的部门)及部门下的员工信息
select * from dept,emp where dept.deptno = emp.deptno(+);
--===========子查询
--1.查询比雇员7654工资高,同时从事和7788的工作一样的员工
select * from emp where sal > (select sal from emp where empno = 7654)
and job = (select job from emp where empno = 7788);
--2.查询每个部门最低工资及最低工资的部门名称和雇员名称
select deptno,min(sal) from emp group by deptno; --查询部门最低工资
select e1.deptno,dname,e1.minsal,e2.ename from (select deptno,min(sal) minsal
from emp group by deptno) e1,emp e2,dept where e1.deptno = dept.deptno
and e1.deptno = e2.deptno and e1.minsal = e2.sal
select * from dept;
select * from emp;
--===========课堂练习
--1.找到员工表中工资最高的前三名
select rownum,emp.* from emp order by sal desc;
select rownum,e.* from (select * from emp order by sal desc) e where rownum <= 3;
--2.找到员工表中薪水大于本部门平均工资的所有员工
select e2.ename,e2.deptno,e2.sal,e1.avgsal from (select deptno,avg(sal) avgsal from emp group by deptno) e1,emp e2
where e1.deptno = e2.deptno and e1.avgsal < e2.sal;
--3.统计每年入职的员工个数
select to_char(hiredate,'yyyy'),count(*) from emp group by to_char(hiredate,'yyyy')
--求出总人数
select sum(e1.hcount) as Total from (select to_char(hiredate,'yyyy') hdate,count(*) hcount from emp group by to_char(hiredate,'yyyy')) e1
--统计每年入职的员工个数
select sum(e1.hcount) as Total,sum(decode(e1.hdate,'1980',e1.hcount)) as "1980",min(decode(e1.hdate,'1981',e1.hcount)) as "1981",max(decode(e1.hdate,'1982',e1.hcount)) as "1982",avg(decode(e1.hdate,'1987',e1.hcount)) as "1987" from (select to_char(hiredate,'yyyy') hdate,count(*) hcount from emp group by to_char(hiredate,'yyyy')) e1
--===========分页查询
--1.查询员工表,将员工工资进行降序查询,并进行分页取出第一页,一页三条记录
select rownum,e.* from (select * from emp order by sal desc) e where rownum <= 3;
--分页公式
select * from (select rownum r,e.* from (select * from emp order by sal desc) e) e1
where e1.r > 3 and e1.r <= 6;
--===========集合运算(了解)
--1.查询工资大于1200并且job是SALESMAN(intersect)
select * from emp where sal > 1200
intersect
select * from emp where job = 'SALESMAN';
--2.查询工资大于1200或者job是SALESMAN(union)
select * from emp where sal > 1200
union
select * from emp where job = 'SALESMAN';
--3.求工资大约1200和job是SALESMAN的差集(minus)
select * from emp where sal > 1200
minus
select * from emp where job = 'SALESMAN';
--==========================exists / not exists
--1.查询出有员工的部门
select * from dept where not exists (select * from emp where emp.deptno = dept.deptno);
select * from dept where 1=1; -- select * from emp where exists (select * from dept)