查询练习
1.查询工资大于12000的员工姓名和工资
select last_name, salary
from employees
where salary > 12000
2.查询员工号为176的员工的姓名和部门号
select last_name, department_id
from employees
where employee_id = 176
3.选择工资不在5000到12000的员工的姓名和工资
select last_name, salary
from employees
where salary not between 5000 and 12000
4.选择雇用时间在1998-02-01到1998-05-01之间的员工姓名，job_id和雇用时间
select last_name, job_id, hire_date
from employees
where hire_date between '1-2月 -1998' and '1-5月 -1998'
5.选择在20或50号部门工作的员工姓名和部门号
select last_name, department_id
from employees
where department_id in (20, 50)
6.选择在1994年雇用的员工的姓名和雇用时间
select last_name, hire_date
from employees
where hire_date like '% -94'
7.选择公司中没有管理者的员工姓名及job_id
select last_name, job_id
from employees
where manager_id is null
8.选择公司中有奖金的员工姓名，工资和奖金级别
select last_name, salary, commission_pct
from employees
where commission_pct is not null
9.选择员工姓名的第三个字母是a的员工姓名
select last_name
from employees
where last_name like '__a%'
10.选择姓名中有字母a和e的员工姓名
select last_name
from employees
where last_name like '%a%' and last_name like '%e%'
11.显示系统时间
select to_char(sysdate,'yyyy-mm-dd hh:mi:ss') from dual;
12.查询员工号，姓名，工资，以及工资提高百分之20%后的结果（new salary）
select employee_id,last_name,salary,salary*1.2 "new salary" from employees;
13.将员工的姓名按首字母排序，并写出姓名的长度（length）
select last_name,length(last_name)
from employees
order by last_name
14.查询各员工的姓名，并显示出各员工在公司工作的月份数（worked_month）。
select last_name,months_between(sysdate,hire_date) worked month from employees
15.查询员工的姓名，以及在公司工作的月份数（worked_month），并按月份数降序排列
select last_name, months_between(sysdate, hire_date) worked_month
from employees
order by worked_month desc
16.做一个查询，产生下面的结果
结果.PNG
select last_name || ' earns ' || salary || ' monthly but wants ' || salary * 3
from employees
17.使用decode函数，按照下面的条件：
decode函数.PNG
select last_name, job_id, decode(job_id, 'AD_PRES', 'A',
'ST_MAN', 'B',
'IT_PROG', 'C',
'SA_REP', 'D',
'ST_CLERK', 'E',
'F') GRADE
from employees
18.将第7题的查询用case函数再写一遍。
select last_name, job_id, case job_id when 'AD_PRES' then 'A'
when 'ST_MAN' then 'B'
when 'IT_PROG' then 'C'
when 'SA_REP' then 'D'
when 'ST_CLERK' then 'E'
else 'F'
end
from employees
19.查询公司员工工资的最大值，最小值，平均值，总和
Select max(salary), min(salary), avg(salary), sum(salary)
From employees
20.查询各job_id的员工工资的最大值，最小值，平均值，总和
Select job_id, max(salary), min(salary), avg(salary), sum(salary)
From employees
Group by job_id
21.选择具有各个job_id的员工人数
Select job_id, count(employee_id)
From employees
Group by job_id;
22.查询员工最高工资和最低工资的差距（DIFFERENCE）
Select max(salary) – min(salary) difference
From employees
23.查询各个管理者手下员工的最低工资，其中最低工资不能低于6000，没有管理者的员工不计算在内
Select manager_id, min(salary)
From employees
Where manager_id is not null
Group by manager_id
Having min(salary) >= 6000
24.查询所有部门的名字，location_id，员工数量和工资平均值
Select department_name, location_id, count(employee_id), avg(salary)
From employees e join departments d
On e.department_id = d.department_id
Group by department_name, location_id
一、找到员工表中工资最高的前三名：
关于行号
1. rownum永远按照默认的顺序生成
2. rownum只能使用 < <=; 不能使用> >=
SQL> select rownum,empno,ename,sal
2 from (select * from emp order by sal desc)
3 where rownum<=3;
ROWNUM EMPNO ENAME SAL
---------- ---------- ---------- ----------
1 7839 KING 5000
2 7788 SCOTT 3000
3 7902 FORD 3000
2.rownum只能使用 < <=; 不能使用> >=
SQL> select *
2 from (select rownum r,e1.*
3 from (select * from emp order by sal) e1
4 where rownum <=8
5 )
6 where r >=5;
临时表:
1. create global temporary table *****
2.自动创建: order by
特点：当事务或者会话结束的时候，表中的数据自动删除
所以 oracle中事务提交了 数据不一定保存下来了（临时表），数据不在，但表还在
SQL> create global temporary table test2
2 (tid number,tname varchar2(20))
3 on commit delete rows;
表已创建。
SQL> insert into test2 values(1,'Tom');
已创建 1 行。
SQL> select * from test2;
TID TNAME
---------- --------------------
1 Tom
SQL> commit;
提交完成。
SQL> select * from test2;
未选定行
SQL> desc test2
名称 是否为空? 类型
----------------------------------------------------------------------------------------------------------------- -------- ----------------------------------------------------------------------------
TID NUMBER
TNAME VARCHAR2(20)
二、找到员工表中薪水大于本部门平均薪水的员工:
相关子查询：将主查询中的值作为参数传递给子查询:
SQL> select empno,ename,sal,(select avg(sal) from emp where deptno=e.deptno) avgsal
2 from emp e
3 where sal > (select avg(sal) from emp where deptno=e.deptno);
EMPNO ENAME SAL AVGSAL
---------- ---------- ---------- ----------
7499 ALLEN 1600 1566.66667
7566 JONES 2975 2175
7698 BLAKE 2850 1566.66667
7788 SCOTT 3000 2175
7839 KING 5000 2916.66667
7902 FORD 3000 2175
解：
SQL> select e.empno,e.ename,e.sal,d.avgsal
2 from emp e,(select deptno,avg(sal) avgsal from emp group by deptno) d
3 where e.deptno=d.deptno and e.sal > d.avgsal;
EMPNO ENAME SAL AVGSAL
---------- ---------- ---------- ----------
7698 BLAKE 2850 1566.66667
7499 ALLEN 1600 1566.66667
7902 FORD 3000 2175
7788 SCOTT 3000 2175
7566 JONES 2975 2175
7839 KING 5000 2916.66667
三、统计每年入职的员工个数
每年入职的员工个数.PNG
SQL> select count(*) Total,
2 sum(decode(to_char(hiredate,'yyyy'),'1980',1,0)) "1980",
3 sum(decode(to_char(hiredate,'yyyy'),'1981',1,0)) "1981",
4 sum(decode(to_char(hiredate,'yyyy'),'1982',1,0)) "1982",
5 sum(decode(to_char(hiredate,'yyyy'),'1987',1,0)) "1987"
6 from emp;
TOTAL 1980 1981 1982 1987
---------- ---------- ---------- ---------- ----------
14 1 10 1 2
1.查询和Zlotkey相同部门的员工姓名和雇用日期
select last_name, hire_date
from employees
where department_id = (
select department_id
from employees
where last_name = 'Zlotkey'
)
2.查询工资比公司平均工资高的员工的员工号，姓名和工资。
select employee_id, last_name, salary
from employees
where salary > (
select avg(salary)
from employees
)
3.查询各部门中工资比本部门平均工资高的员工的员工号, 姓名和工资
select employee_id, last_name, salary
from employees e
where salary > (
select avg(salary)
from employees
where department_id = e.department_id
)
4.查询和姓名中包含字母u的员工在相同部门的员工的员工号和姓名
select employee_id, last_name
from employees
where department_id in (
select department_id
from employees
where last_name like '%u%'
)
5.查询在部门的location_id为1700的部门工作的员工的员工号，
select employee_id
from employees
where department_id in (
select department_id
from departments
where location_id = 1700
)
6.查询管理者是King的员工姓名和工资
select last_name, salary
from employees
where manager_id in (
select employee_id
from employees
where last_name = 'King'
)