Question

Well, I got table Workers in my DB. There are 4 columns id,name,salary and department. I need to show list of departments where count of workers with salary more than 90% of max salary value in row and where count of workers with such salary is more than 15% of workers count in department.

At first I made such query which shows all rows with workers who have big salary

 SELECT * 
 FROM   `Workers` 
 WHERE id IN (
    SELECT `id`  
    FROM   `Workers` 
    WHERE  `salary` > 0.9 * (SELECT MAX( `salary` )
                             FROM  `Workers`)) 

Maybe I asking really silly thing but I stuck and i don’t know really how to make next step to throw from it workers who have big salary but in their departments are less than 15% got salaries like this.

Answer 1

This is ugly but it should work:

SELECT department, COUNT(*)
FROM `Workers` w
WHERE id IN
    (SELECT `id`  FROM `Workers`
     WHERE  `salary` > 0.9 * (SELECT MAX( `salary` )  FROM  `Workers`)) 
GROUP BY department
HAVING COUNT(*) > 0.15 *
    (SELECT COUNT(*) FROM `Workers`
     WHERE department = w.department)