MySQL【案例讲解】分组查询
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MySQL【案例讲解】分组查询
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#1.查詢各job_id的員工工資的最大值,最小值,平均值,總和,并按job_id升序
SELECT MAX(salary), MIN(salary), AVG(salary), SUM(salary), job_id FROM employees GROUP BY job_id ORDER BY job_id;#2.查詢員工最高工資和最低工資的差距(DIFFERENCE)
SELECT MAX(salary) - MIN(salary) DIFFERENCE FROM employees;#3.查詢各個管理者手下員工的最低工資,其中最低工資不能低于6000,沒有管理者的員工不計算在內
SELECT MIN(salary), manager_idFROM employeesWHERE manager_id IS NOT NULLGROUP BY manager_idHAVING MIN(salary)>=6000;#4.查詢所有部門的編號,員工數量和工資平均值,并按平均工資降序
SELECT department_id, COUNT(*), AVG(salary) FROM employees GROUP BY department_id ORDER BY AVG(salary) DESC;#5.選擇具有各個job_id的員工個數???????
SELECT COUNT(*), job_id FROM employees GROUP BY job_id;總結
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