Q:

Selecting the Max Value from Each Unique Day for Multiple Locations

I have a table with the following structure (note the headers are actually all caps):
Start_Date | Hour | Item | Location | ... | Numerical Metrics ... |
-----------|------|------|----------|-----|-----------------------|
8/6/19     |  0   |   A  |    USE   | ... | (numbers that I want  |
8/6/19     |  0   |   B  |    USE   | ... |  to get the max of)   |
8/6/19     |  0   |   C  |    USW   | ... |                       |
8/6/19     |  0   |   D  |    USW   | ... |                       |
8/6/19     |  1   |   A  |    USE   | ... |                       |
8/6/19     |  1   |   B  |    USE   | ... |                       |
8/6/19     |  1   |   C  |    USW   | ... |                       |
8/6/19     |  1   |   D  |    USW   | ... |                       |
.....
8/1/19     |  23  |   D  |    USW   | ... |                       |

This continues, Hours 0 - 23 (4x each; 1x for each item) for every date.  So there's 96 data points (rows) per day
I'm trying to query (or create a new table) and present the max data from the numerical metrics for each unique day for each item.  So if I had the dates: 8/1/19 -> 8/6/19, I currently have 576 rows, but I'm trying to break that down to the 4 for each day, or 24 rows. 
I'm currently just trying to get the max for each specific day (so not even worried about the Item portion yet -- which I can't get either) but when I put MAX in my SELECT statements I'm only getting 1 result overall.  So I'm having a hard time figuring out how to "loop" through all dates and grab each one.  I'm tried UNIQUE Start_Date to see if that would give me a max for each date, but that didn't work either.  
SELECT START_DATE,
       HOUR,
       ITEM,
       LOCATION,
       SERVICE,
       MAX(SALES)                            as SALES,
       MAX(ITEMS)                             as ITEMS,
       MAX(PRICE)                              as PRICE,
FROM newtable
WHERE ITEM IN (
        SELECT ITEM
        FROM newtable
        WHERE START_DATE IN (
                SELECT DISTINCT START_DATE
                FROM newtable
        )
);

The results I would be looking for are:
Start_Date | Item | Location | ... | Numerical Metrics ... |
-----------|------|----------|-----|-----------------------|
8/6/19     |   A  |    USE   | ... | (max numbers from     |
8/6/19     |   B  |    USE   | ... |  that day are shown)  |
8/6/19     |   C  |    USW   | ... |                       |
8/6/19     |   D  |    USW   | ... |                       |
8/5/19     |   A  |    USE   | ... |                       |

we can rid of the hour table since I no longer care about it, the goal is to obtain a daily metric
The current result is just the first row:
Start_Date | Item | Location | ... | Numerical Metrics ... |
-----------|------|----------|-----|-----------------------|
8/6/19     |   A  |    USE   | ... | max from that day     |

A:

I'm trying to query (or create a new table) and present the max data from the numerical metrics for each unique day for each item.  

This is an aggregation query:
SELECT START_DATE, ITEM,
       MAX(SALES) as SALES,
       MAX(ITEMS as ITEMS,
       MAX(PRICE) as PRICE
FROM newtable
GROUP BY START_DATE, ITEM;

Including the location and other (non-aggregated) columns doesn't make sense for the question you are asking.