oracle基本查询练习

select * from regions;
select * from countries;
select * from locations;
select * from departments;
select * from jobs;
select * from employees;
select * from job_history;

1. 查询工资大于12000的员工姓名和工资
select '姓名:' || first_name || last_name || ',工资:' || 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 first_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 first_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 first_name, job_id, hire_date
   from employees
  where hire_date between to_date('1998-02-01', 'yyyy-mm-dd') and
        to_date('1998-05-01', 'yyyy-mm-dd');

5. 选择在20或50号部门工作的员工姓名和部门号
select first_name, 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 first_name, last_name, hire_date
   from employees
  where to_char(hire_date, 'yyyy') = 1994;

7. 选择公司中没有管理者的员工姓名及job_id
select first_name, 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||' '||first_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 first_name, last_name from employees where first_name like '__a%';

10. 选择姓名中有字母a和e的员工姓名
select first_name || ' ' || last_name
   from employees
  where first_name || last_name like '%a%e'
     or last_name || first_name like '%e%a';--为什么firts_name和last_name要倒置写一次??

11. 显示系统时间
select sysdate 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 * from employees;
select employee_id, first_name||' '||last_name, salary, salary * 1.2 as "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 initcap(concat(first_name,last_name)) "name",
        length(concat(first_name, last_name)) "length"
   from employees
  order by substr(concat(first_name, last_name), 1, 1);

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
select initcap(concat(first_name, last_name)) "name",
        round(months_between(sysdate, hire_date)) "month"
   from employees
  order by substr(concat(first_name, last_name), 1, 1);

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 initcap(concat(first_name, last_name)) "name",
        round(months_between(sysdate, hire_date)) "worked_month"
   from employees
  order by "worked_month";