#查询和Zlotkey相同部门的员工姓名和工资

SELECT last_name,salary
FROM employees
WHERE department_id=(
    SELECT department_id
    FROM employees
    WHERE last_name='Zlotkey'
);

#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
);

#查询各部门中工资比本部门平均工资高的员工号、姓名和工资
注：连接员工表和平均工资表，再筛选

SELECT employee_id,last_name,salary
FROM (
    SELECT AVG(salary) s,department_id
    FROM employees 
    GROUP BY department_id
) a
INNER JOIN employees e
ON a.department_id=e.department_id
WHERE e.salary>s;

#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
先查询包含u员工的部门id，再查id相同情况

SELECT employee_id,last_name
FROM employees
WHERE department_id IN(
    SELECT DISTINCT department_id
    FROM employees
    WHERE last_name LIKE '%u%'
);

#查询在部门的location_id为1700的部门工作的员工的员工号
注先查询location_id等于1700的部门编号，在查询员工号

SELECT employee_id
FROM employees e
WHERE e.`department_id` IN(
    SELECT department_id
    FROM departments d
    WHERE d.`location_id`=1700
)

#查询管理者是K_ing的员工姓名和工资,有两个K_ing

SELECT last_name,salary
FROM employees e
WHERE e.manager_id IN(
    SELECT `employee_id`
    FROM employees m
    WHERE `last_name`='K_ing'
);

#查询工资最高的员工的姓名，要求first_ame和last_name 显示为一列，列名为 姓.名
#起别名有特殊字符需要用引号括起来

SELECT CONCAT(first_name,last_name) '姓.名'  
FROM employees e
WHERE e.salary=(
    SELECT MAX(salary)
    FROM employees
);