SELECT count(),department_id from employees GROUP BY department_id HAVING count()>2;
#按表达式进行分组 SELECT count() ,LENGTH(last_name) from employees GROUP BY LENGTH(last_name) HAVING count()>5 ORDER BY LENGTH(last_name) asc;
#按多个字段分组 SELECT AVG(salary) ,department_id,job_id from employees GROUP BY department_id,job_id HAVING AVG(salary)>5000;
#分组查询排序 SELECT AVG(salary) ,department_id,job_id from employees where department_id is not NULL GROUP BY department_id,job_id HAVING AVG(salary)>10000 ORDER BY AVG(salary) DESC;
SELECT max(salary)-min(salary) from employees
SELECT min(salary) , manager_id from employees where manager_id is not null GROUP BY manager_id HAVING min(salary)>6000
SELECT department_id ,count(*),ROUND(AVG(salary),2) from employees where department_id is not null GROUP BY department_id ORDER BY AVG(salary) desc;
SELECT count(*),job_id from employees where job_id is not null GROUP BY job_id
