#第13章 MySQL8的新特性（可选拓展）

函数名([参数列表]) OVER ()
函数名([参数列表]) OVER (子句)

rank() over ()
rank() over (order by salary)
rank() over (PARTITION BY did)
rank() over (PARTITION BY did order by salary)

#（1）在“t_employee”表中查询薪资在[8000,10000]之间的员工姓名和薪资并给每一行记录编序号
SELECT ROW_NUMBER() OVER () AS "row_num",ename,salary
FROM t_employee WHERE salary BETWEEN 8000 AND 10000;

#（2）计算每一个部门的平均薪资与全公司的平均薪资的差值。
SELECT  did,AVG(salary) OVER() AS avg_all,
AVG(salary) OVER(PARTITION BY did) AS avg_did,
ROUND(AVG(salary) OVER()-AVG(salary) OVER(PARTITION BY did),2) AS deviation
FROM  t_employee;


#（3）在“t_employee”表中查询女员工姓名，部门编号，薪资，查询结果按照部门编号分组后在按薪资升序排列，并分别使用ROW_NUMBER（）、RANK（）、DENSE_RANK（）三个序号函数给每一行记录编序号。
SELECT ename,did,salary,gender,
ROW_NUMBER() OVER (PARTITION BY did ORDER BY salary) AS "row_num",
RANK() OVER (PARTITION BY did ORDER BY salary) AS "rank_num" ,
DENSE_RANK() OVER (PARTITION BY did ORDER BY salary) AS "ds_rank_num" 
FROM t_employee WHERE gender='女';

#或

SELECT ename,did,salary,
ROW_NUMBER() OVER w AS "row_num",
RANK() OVER w AS "rank_num" ,
DENSE_RANK() OVER w AS "ds_rank_num" 
FROM t_employee WHERE gender='女'
WINDOW w AS (PARTITION BY did ORDER BY salary);


#（4）在“t_employee”表中查询每个部门最低3个薪资值的女员工姓名，部门编号，薪资值。
SELECT ROW_NUMBER() OVER () AS "rn",temp.*
FROM(SELECT ename,did,salary,
ROW_NUMBER() OVER w AS "row_num",
RANK() OVER w AS "rank_num" ,
DENSE_RANK() OVER w AS "ds_rank_num" 
FROM t_employee WHERE gender='女'
WINDOW w AS (PARTITION BY did ORDER BY salary))temp 
WHERE temp.rank_num<=3;

#或
SELECT ROW_NUMBER() OVER () AS "rn",temp.*
FROM(SELECT ename,did,salary,
ROW_NUMBER() OVER w AS "row_num",
RANK() OVER w AS "rank_num" ,
DENSE_RANK() OVER w AS "ds_rank_num" 
FROM t_employee WHERE gender='女'
WINDOW w AS (PARTITION BY did ORDER BY salary))temp 
WHERE temp.ds_rank_num<=3;


#（5）在“t_employee”表中查询每个部门薪资排名前3的员工姓名，部门编号，薪资值。
SELECT temp.*
FROM(SELECT ename,did,salary,
DENSE_RANK() OVER w AS "ds_rank_num" 
FROM t_employee
WINDOW w AS (PARTITION BY did ORDER BY salary DESC))temp 
WHERE temp.ds_rank_num<=3;

#（6）在“t_employee”表中查询全公司薪资排名前3的员工姓名，部门编号，薪资值。
SELECT temp.*
FROM(SELECT ename,did,salary,
DENSE_RANK() OVER w AS "ds_rank_num" 
FROM t_employee
WINDOW w AS (ORDER BY salary DESC))temp 
WHERE temp.ds_rank_num<=3;

WITH [RECURSIVE]
 cte_name [(col_name [, col_name] ...)] AS (subquery)
 [, cte_name [(col_name [, col_name] ...)] AS (subquery)]
 ...

#（1）在“t_employee”表中查询每个人薪资和公司平均薪资的的差值。
WITH temp AS (SELECT AVG(salary) AS pingjun FROM t_employee)
SELECT ename AS "员工姓名",
    salary AS "薪资",
    ROUND(pingjun,2) "公司平均薪资",
    ROUND(salary - pingjun,2) "差值"
FROM t_employee,temp
HAVING ABS(差值)>5000;

#（2）查询薪资低于9000的员工编号，员工姓名，员工薪资，领导编号，领导姓名，领导薪资
WITH 
emp AS (SELECT eid,ename,salary,`mid` FROM t_employee WHERE salary <9000),
mgr(meid,mename,msalary) AS (SELECT eid,ename,salary FROM t_employee)
  
SELECT eid AS "员工薪资",
	ename AS "员工姓名",
	salary AS "员工薪资",
	meid AS "领导编号",
	mename AS "领导姓名",
	msalary AS "领导薪资"
FROM emp INNER JOIN mgr ON emp.mid = mgr.meid;

#（3）查询eid为21的员工，和他所有领导，直到最高领导。
with recursive temp as (
	SELECT * FROM `t_employee` where eid = 5
	union
	select t_employee.* 
	from t_employee inner join temp
	on t_employee.eid = temp.mid
)
select * from temp;