MSSQL寫法~參考~

create table Tmp(
進貨單號 nvarchar(50) 
,進貨日期 nvarchar(50) 
,產品型號 nvarchar(50) 
,數量 int
);
insert into Tmp
values('190814001','20190722','A0001','29')
,('190828004','20190830','A0001','345')
,('200803003','20200803','A0001','345')
,('200821002','20200812','A0001','338');

select *
from Tmp

select 進貨單號
,進貨日期
,產品型號
,數量
from (
  select Row_Number()over(PARTITION BY 產品型號,left(進貨日期,6) order by 進貨日期 desc) Sort
  ,*
  from Tmp
) k
where Sort = 1

https://dbfiddle.uk/?rdbms=sqlserver_2019&fiddle=f00cedc1e3571f509a28cafcd190109b

用max吧
至於要不要DATE_FORMAT看你資料結構決定

SELECT *, MAX(DATE_FORMAT(date_column_name, '%y%m'))  FROM `table` 
GROUP BY DATE_FORMAT(date_column_name, '%y%m')

//https://www.w3schools.com/sql/func_mysql_max.asp

SELECT 
  YEAR(進貨日期) AS Y
  ,MONTH(進貨日期) AS M
  ,MAX(進貨日期)
  FROM [dbo].進貨表
  GROUP BY YEAR(進貨日期), MONTH(進貨日期)