分析函數 —— Avg移動開窗的一些思考和探索

導火索：求出的是移動平均：

select t2.*
      ,avg(t2.amt)over(partition by dimShopID order by amt  desc) as a1
from (select t1.dimShopID
      ,t1.dimDateID
      ,sum(AMT) as amt
from dw.fct_sales t1
where dimDateID between 20170801 and 20170810
group by t1.dimShopID
      ,t1.dimDateID) t2     

-- 輸出結果：
#	dimShopID	dimDateID	amt	a1
1	33	20,170,803	75,431.34	75,431.34
2	33	20,170,801	65,459.27	70,445.305
3	33	20,170,804	63,718.71	68,203.106666666
4	33	20,170,802	58,404.6	65,753.48
5	33	20,170,807	56,704.89	63,943.762
6	33	20,170,806	52,233.34	61,992.025
7	33	20,170,810	46,969.19	59,845.905714285
8	33	20,170,808	46,852.21	58,221.69375
9	33	20,170,809	45,016.49	56,754.448888888
10	33	20,170,805	37,233.64	54,802.368
11	34	20,170,803	114,570.17	114,570.17
12	34	20,170,801	79,596.28	97,083.225
13	34	20,170,804	73,828.05	89,331.5
14	34	20,170,806	65,252.32	83,311.705
15	34	20,170,802	64,027.97	79,454.958
16	34	20,170,807	52,923.21	75,033
17	34	20,170,809	47,571.3	71,109.9
18	34	20,170,810	47,543.23	68,164.06625
19	34	20,170,805	44,916.38	65,580.99
20	34	20,170,808	44,691.52	63,492.043

變式1：可用於組內比較

-- 變式1：可用於組內比較

-- 應用：
-- (1)求出每個科目成績大於該科目平均成績的學生;
-- (2)在該份數據中，就可以用來求,每個門店銷售總額高於平均總額的日期
 
SELECT  * 
FROM
(select t2.*
      ,avg(t2.amt)over(partition by dimShopID ) as a1 -- 計算的窗口的平均數
from (select t1.dimShopID
      ,t1.dimDateID
      ,sum(AMT) as amt
from dw.fct_sales t1
where dimDateID between 20170801 and 20170810
group by t1.dimShopID
      ,t1.dimDateID) t2 
)t
where amt > a1 -- where限定行，需要新建一個子查詢

-- 輸出結果：

行號	dimShopID	dimDateID	amt	a1
1	33	20,170,801	65,459.27	54,802.368
2	33	20,170,802	58,404.6	54,802.368
3	33	20,170,803	75,431.34	54,802.368
4	33	20,170,804	63,718.71	54,802.368
5	33	20,170,807	56,704.89	54,802.368
6	34	20,170,801	79,596.28	63,492.043
7	34	20,170,802	64,027.97	63,492.043
8	34	20,170,803	114,570.17	63,492.043
9	34	20,170,804	73,828.05	63,492.043
10	34	20,170,806	65,252.32	63,492.043

變式2:分析函數中不使用 partion by,僅僅使用 order by

-- 變式2:分析函數中不使用 partion by,僅僅使用 order by

select t2.*
      ,avg(t2.amt)over(order by amt  desc) as a1
from (select t1.dimShopID
      ,t1.dimDateID
      ,sum(AMT) as amt
from dw.fct_sales t1
where dimDateID between 20170801 and 20170810
group by t1.dimShopID
      ,t1.dimDateID) t2;
      
-- 輸出：
#	dimShopID	dimDateID	amt	a1
1	34	20,170,803	114,570.17	114,570.17
2	34	20,170,801	79,596.28	97,083.225
3	33	20,170,803	75,431.34	89,865.93
4	34	20,170,804	73,828.05	85,856.46
5	33	20,170,801	65,459.27	81,777.022
6	34	20,170,806	65,252.32	79,022.905
7	34	20,170,802	64,027.97	76,880.771428571
8	33	20,170,804	63,718.71	75,235.51375
9	33	20,170,802	58,404.6	73,365.412222222
10	33	20,170,807	56,704.89	71,699.36
11	34	20,170,807	52,923.21	69,992.437272727
12	33	20,170,806	52,233.34	68,512.5125
13	34	20,170,809	47,571.3	66,901.65
14	34	20,170,810	47,543.23	65,518.905714285
15	33	20,170,810	46,969.19	64,282.258
16	33	20,170,808	46,852.21	63,192.88
17	33	20,170,809	45,016.49	62,123.680588235
18	34	20,170,805	44,916.38	61,167.719444444
19	34	20,170,808	44,691.52	60,300.551052631
20	33	20,170,805	37,233.64	59,147.2055

VS 變式2：

-- 實現效果同變式2,只是多了一個移動平均列
-- 實際過程，沒啥意義
     
select t1.dimShopID
      ,t1.dimDateID
      ,sum(AMT) as amt
from dw.fct_sales t1
where dimDateID between 20170801 and 20170810
group by t1.dimShopID
      ,t1.dimDateID
order by amt desc ; 

-- 輸出結果：
#	dimShopID	dimDateID	amt
1	34	20,170,803	114,570.17
2	34	20,170,801	79,596.28
3	33	20,170,803	75,431.34
4	34	20,170,804	73,828.05
5	33	20,170,801	65,459.27
6	34	20,170,806	65,252.32
7	34	20,170,802	64,027.97
8	33	20,170,804	63,718.71
9	33	20,170,802	58,404.6
10	33	20,170,807	56,704.89
11	34	20,170,807	52,923.21
12	33	20,170,806	52,233.34
13	34	20,170,809	47,571.3
14	34	20,170,810	47,543.23
15	33	20,170,810	46,969.19
16	33	20,170,808	46,852.21
17	33	20,170,809	45,016.49
18	34	20,170,805	44,916.38
19	34	20,170,808	44,691.52
20	33	20,170,805	37,233.64