-- 1. 查询员工表所有数据，并说明使用*的缺点
SELECT * from employees
-- *号查询效率低
-- 2. 查询所员工的 email 全名,公司 email 统一以 "@qq.com " 结尾.
SELECT email from employees WHERE email like "%@qq.com"
-- 3. 打印公司里所有的 manager_id(去除重复数据)
select distinct manager_id from employees
-- 4. 查询职位(JOB_ID)为'ST_CLERK'的员工的工资
SELECT salary from employees WHERE JOB_ID="ST_CLERK"
-- 5. 查询 50 号部门的员工姓名.
SELECT last_name from employees WHERE department_id=50
-- 6. 查询 80 号部门工资大于 7000 的员工的全名.
SELECT first_name,last_name from employees WHERE department_id=50 and salary>7000
-- 7. 查询工资高于 7000 但是没有提成的所有员工.
SELECT * from employees WHERE commission_pct=null and salary>7000
-- 8. 查询入职日期在 1997-5-1 到 1997-12-31 之间的所有员工信息
-- SELECT * from employees WHERE hiredate between '1997-5-1' and '1997-12-31'
select *
from employees
where hiredate between str_to_date('1997-5-1','%Y-%m-%d') and str_to_date('1997-12-31','%Y-%m-%d')
-- 9. 显示姓名中没有'L'字的员工的详细信息
SELECT * from employees WHERE first_name not like "%L%"
-- 10. 查询电话号码以 8 开头的所有员工信息.
SELECT * from employees WHERE phone_number like "8%"
-- 11. 查询 80 号部门中 last_name 以 n 结尾的所有员工信息
SELECT * from employees WHERE department_id=80 and last_name like "%n"
-- 12. 查询所有 last_name 由四个以上字母组成的员工信息
SELECT * from employees WHERE first_name like '____'
select * from employees where LENGTH(last_name)>4
-- 13. 查询 first_name 中包含"na"的员工信息.
SELECT * from employees WHERE first_name like '%na%'
-- 14. 显示公司里所有员工的工资级别 case when
select employee_id, salary,
CASE
when salary>=15000 then'D'
when salary>=8001 or salary>=15000 then'B'
when salary>=5001 or salary>=8000 then'A'
else 'A'
END as '工资标准'
from employees
-- 15 根据入职时间打印出员工级别
select hiredate,
case
when date_format(hiredate,'%Y')>1990 then '新员工'
when date_format(hiredate,'%Y')>=1986 then'普通员工'
when date_format(hiredate,'%Y')<=1985 then '资深员工'
end as 员工级别
from employees
-- 请打印出 1997 年入职的员工
select first_name from employees where date_format(hiredate,'Y')=1978
-- 把 hiredate 列看做是员工的生日,求本月过生日的员工
select * from employees where date_format(now(),'%m')=date_format(hiredate,'%m')
-- 查询入职时间超过25年的员工信息
select * from employees where date_format(now(),'%Y')-date_format(hiredate,'%Y')>'25'
-- 以 员工id-员工完整姓名-员工工资 的形式查询员工信息
select employee_id,salary,concat(first_name,last_name) from employees
-- 查询工资高于10000并且岗位id长度小于5的员工信息
select * from employees where salary>10000 and length(job_id)<=5