如何获得平均开始的第三个前记录作为列包含到当前行？

Question

我有如下一些数据：

id	date	code	price
892	2022-02-04	B	472
891	2022-02-03	B	58
890	2022-02-02	B	467
868	2022-01-28	B	50
821	2022-01-23	B	45
780	2022-01-20	B	55
550	2022-01-14	B	79
245	2022-01-12	B	841
112	2022-01-11	B	128
91	2022-01-07	B	174
74	2022-01-04	B	64

我想获得三个记录的平均价格，从前第三行开始在一个 SQL 查询中包含到当前行，所以我期望如下所示：

id	date	code	price	avg3th
892	2022-02-04	B	472	average of ( 467+50+45)
891	2022-02-03	B	58	average of ( 50+45+55)
890	2022-02-02	B	467	average of ( 50+45+79)
868	2022-01-28	B	50	average of ( 45+79+841)
821	2022-01-23	B	45	average of ( 79+841+128)
780	2022-01-20	B	55	average of ( 841+128+174)
550	2022-01-14	B	79	...
245	2022-01-12	B	841	...
112	2022-01-11	B	128	...
91	2022-01-07	B	174	...
74	2022-01-04	B	64	...

我已经尝试过，使用以下查询：

SELECT t.id, t.date, t.code, t.price,
format(
 CASE WHEN
    ROW_NUMBER() OVER (ORDER BY t.date) >=5 THEN
         AVG ( t.price ) OVER (ORDER BY t.date
            ROWS BETWEEN 4 PRECEDING AND 2 FOLLOWING)
    ELSE NULL
 END,0) AS average_3th
FROM test t ORDER BY t.id DESC

但是，上面的查询仍然包括第一个元素作为平均值（它应该从第三个元素开始），所以下面的结果仍然是错误的：

有什么想法吗？

Answer 1

在子查询中使用行数idea average

WITH CTE AS
(SELECT T.*,ROW_NUMBER() OVER (PARTITION BY CODE ORDER BY ID DESC) RN FROM T ),
CTE1 AS
(SELECT T.*,ROW_NUMBER() OVER (PARTITION BY CODE ORDER BY ID DESC) RN FROM T )
SELECT CTE.*,
         (SELECT AVG(CTE1.PRICE) FROM CTE1 WHERE CTE1.CODE = CTE.CODE AND CTE1.RN BETWEEN CTE.RN + 2 AND CTE.RN + 4),
          (SELECT GROUP_CONCAT(CTE1.ID) FROM CTE1 WHERE CTE1.CODE = CTE.CODE AND CTE1.RN BETWEEN CTE.RN + 2 AND CTE.RN + 4)
FROM CTE
ORDER BY CTE.ID DESC
;

https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=437342579b3165f31292e288e3165bed

如何获得平均开始的第三个前记录作为列包含到当前行？

How to get average starting third previous record to be included to current row as column?

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