[SQLServer] I have a table and sample data:
CREATE TABLE ApiUsage
(
    DBPK INT IDENTITY,
    CallDate DATE NOT NULL DEFAULT(GETDATE()),
    CallCount INT
)

INSERT INTO dbo.ApiUsage VALUES('2020-05-01', 4)
INSERT INTO dbo.ApiUsage VALUES('2020-05-01', 3)
INSERT INTO dbo.ApiUsage VALUES('2020-05-02', 2)
INSERT INTO dbo.ApiUsage VALUES('2020-05-02', 8)
INSERT INTO dbo.ApiUsage VALUES('2020-05-02', 1)
INSERT INTO dbo.ApiUsage VALUES('2020-05-03', 5)
INSERT INTO dbo.ApiUsage VALUES('2020-05-03', 2)

I want to query the cumulative results per day:
2020-05-01 => 7
2020-05-02 => 18 (7+11)
2020-05-03 => 25 (7+11+7)


 help me write a query statement, but I need the result to be:

Day         Total
2020-05-01  7
2020-05-02  18
2020-05-03  25

I try to write sql to implement this:
SELECT 
    CallDate, 
    SUM(CallCount) OVER (PARTITION BY CallDate ORDER BY ROW_NUMBER() OVER (PARTITION BY CallDate ORDER BY CallDate)) AS Total
FROM 
    ApiUsage


but error shows:
Msg 4109, Level 15, State 1, Line 4
Windowed functions cannot be used in the context of another windowed function or aggregate.


and I also tried :
WITH cte AS (
    SELECT 
        CallDate, 
        CallCount,
        SUM(CallCount) OVER (ORDER BY CallDate) AS RunningTotal
    FROM 
        ApiUsage
)
SELECT 
    CallDate, 
    RunningTotal AS Total
FROM 
    cte
and result shows
CallDate	Total
2020-05-01	7
2020-05-01	7
2020-05-02	18
2020-05-02	18
2020-05-02	18
2020-05-03	25
2020-05-03	25
also incorrect