#1.查詢工資最低的員工資訊：last name, salary

 SELECT

     last_name,

     salary

 FROM

     employees

 WHERE

     salary = (

         SELECT

             MIN(salary)

         FROM

             employees

     );

 #2.查詢平均工資最低的部門資訊

 SELECT

     *

 FROM

     departments

 WHERE

     department_id = (

         SELECT
 

             department_id

         FROM

             employees

         GROUP BY

             department_id

         ORDER BY

             avg(salary)

         LIMIT 1

     );

 #3.查詢平均工資最低的部門資訊和該部門的平均工資

 #①各部門的平均工資

 SELECT

     avg(salary),

     department_id

 FROM

     employees

 GROUP BY

     department_id #②求出最低平均工資的部門編號
 

     SELECT

         avg(salary),

         department_id

     FROM

         employees

     GROUP BY

         department_id

     ORDER BY

         avg(salary)

     LIMIT 1;

 #③查詢部門資訊

 SELECT

     d.*, ag

 FROM

     departments d

 JOIN (

     SELECT

         avg(salary),

         department_id

     FROM
 

         employees

     GROUP BY

         department_id

     ORDER BY

         avg(salary)

     LIMIT 1

 ) ag_dep ON d.department_id = ag_dep.department_id #4.查詢平均工資最高的job資訊

 SELECT

     avg(salary)

 FROM

     employees

 GROUP BY

     job_id

 ORDER BY

     avg(salary) DESC

 LIMIT 1 ②查詢job資訊 SELECT

     *

 FROM

     jobs

 WHERE

     job_id = (

         SELECT

             job_id

         FROM

             employees

         GROUP BY

             job_id

         ORDER BY

             avg(salary) DESC

         LIMIT 1

     );

 #5.查詢平均工資高於公司平均工資的部門有哪些？

 SELECT

     avg(salary),

     department_id

 FROM

     employees

 GROUP BY

     department_id;

 HAVING

     avg(salary) > (

         SELECT

             avg(salary)

         FROM

             employees

     );

 #6.查詢出公司中所有 manager的詳細資訊

 SELECT

     *

 FROM

     employees

 WHERE

     employee_id IN (

         SELECT DISTINCT

             manager_id

         FROM

             employees

     );

 #7.各個部門中最高工資中最低的那個部門的最低工資是多少

 SELECT

     min(salary),

     department_id

 FROM

     employees

 WHERE

     department_id = (

         SELECT

             department_id

         FROM

             employees

         GROUP BY

             department_id

         ORDER BY

             max(salary)

         LIMIT 1

     );

 #8.查詢平均工資最高的部門的 manager的詳細資訊：last_name, department id, email

 SELECT

     last_name,

     d.department_id,

     email,

     salary

 FROM

     employees e

 JOIN departments d ON d.manager_id = e.manager_id

 WHERE

     d.department_id = (

         SELECT

             department_id

         FROM

             employees

         GROUP BY

             department_id

         ORDER BY

             avg(salary) DESC

         LIMIT 1

     );