MSSQL - How to support aggregate pushdown on indexed view with SUM(decimal)
If you can change the query itself to use the view + NOEXPAND, this can work:

Table definition and test data

CREATE TABLE [dbo].[myTable](
    [ItemId] [int] PRIMARY KEY NOT NULL,
    [BusinessDate] [date] NULL,
    [Gross] [decimal](18, 6) NULL
    );


INSERT INTO 
[dbo].[myTable] WITH(TABLOCK)
(BusinessDate,Itemid,Gross)
SELECT
TOP(5000000) CAST(getdate() AS DATE),
ROW_NUMBER() OVER(ORDER BY (SELECT NULL)),
11.2142
FROM master..spt_values
CROSS APPLY master..spt_values spt2;


View definition + indexes

CREATE VIEW [dbo].[SalesAggregated] with schemabinding AS
        SELECT 
            BusinessDate, 
            ItemId
            ,COUNT_BIG(*) AS NumberOfRows
            ,CAST(SUM(Gross) as [decimal](18, 6))  AS Gross
        FROM [dbo].[myTable]
        GROUP BY BusinessDate, ItemId
GO

CREATE UNIQUE CLUSTERED INDEX CX_ItemId
ON dbo.[SalesAggregated](ItemId);

CREATE NONCLUSTERED COLUMNSTORE INDEX [IX_SalesAggregated] ON [dbo].[SalesAggregated]
(
[Gross],
BusinessDate

);


Query

SELECT SUM(Gross)
FROM [dbo].[SalesAggregated] WITH(NOEXPAND)
WHERE BusinessDate = '2019-08-14';


Result



Properties of the scan with the locally aggreggated rows &amp; batch mode:



Querying the view + WITH(NOEXPAND) is necessary to make this example work.

There are many other reasons why you should use WITH(NOEXPAND). More reasons in this blogpost by Paul White