tsql - t-sql 将追踪平均值与当前数据进行比较

Question

我有一项任务是获取在
过去 10 个月和本月的记录数。例如，在集合中
在以下记录中，过去三个月的平均每月记录为 4.33。
本月的记录数为3。
因此预期的结果是，

declare @recordsReceived table (id int, dob date)

INSERT @recordsReceived VALUES (1,'2020-01-01')
INSERT @recordsReceived VALUES (2,'2020-01-08')
INSERT @recordsReceived VALUES (3,'2020-01-17')
INSERT @recordsReceived VALUES (5,'2020-02-03')
INSERT @recordsReceived VALUES (6,'2020-02-09')
INSERT @recordsReceived VALUES (7,'2020-02-16')
INSERT @recordsReceived VALUES (8,'2020-02-21')
INSERT @recordsReceived VALUES (9,'2020-02-28')
INSERT @recordsReceived VALUES (10,'2020-03-01')
INSERT @recordsReceived VALUES (11,'2020-03-07')
INSERT @recordsReceived VALUES (12,'2020-03-21')
INSERT @recordsReceived VALUES (13,'2020-03-28')
INSERT @recordsReceived VALUES (14,'2020-04-03')
INSERT @recordsReceived VALUES (15,'2020-04-09')
INSERT @recordsReceived VALUES (16,'2020-04-30')
INSERT @recordsReceived VALUES (5,'2020-02-03')
INSERT @recordsReceived VALUES (6,'2020-02-09')
INSERT @recordsReceived VALUES (7,'2020-02-16')
INSERT @recordsReceived VALUES (8,'2020-02-21')
INSERT @recordsReceived VALUES (9,'2020-02-28')
INSERT @recordsReceived VALUES (10,'2020-03-01')
INSERT @recordsReceived VALUES (12,'2020-03-21')
INSERT @recordsReceived VALUES (12,'2020-03-21')
INSERT @recordsReceived VALUES (13,'2020-03-28')
INSERT @recordsReceived VALUES (14,'2020-04-03')
INSERT @recordsReceived VALUES (15,'2020-04-09')
INSERT @recordsReceived VALUES (16,'2020-04-30')

Answer 1

你可以试试这个

Select * From (
  Select count(month(dob))*1.00/count(distinct(month(dob))) As [TAVG] 
  from @recordsReceived 
  Where month(dob)  < (Select max(month(dob)) from @recordsReceived)) A

 ,
 (Select count(month(dob)) [Current]
 from @recordsReceived 
 Where month(dob)  = (Select max(month(dob)) from @recordsReceived)) B