Struggling with a nested where, group by and min/max in SQL

Question

I have this table in MS Access and need to write a query for a report and am struggling. My SQL is largely unused for at least 5 years, and was never really that good, but I thought I could do this without too much trouble...alas.

Product	ProductSubCode	OrderDateTime	Order Amount
A	1	2021-05-25 11:30	5
A	2	2021-05-25 12:30	50
A	1	2021-05-25 13:30	500
B	1	2021-05-25 09:30	400
B	2	2021-05-25 10:30	40
B	1	2021-05-25 11:30	4
C	1	2021-05-25 13:30	30
C	1	2021-05-25 14:30	300
C	2	2021-05-25 15:30	3
A	2	2021-05-24 11:30	5
A	2	2021-05-24 12:30	50
A	1	2021-05-24 13:30	500
B	1	2021-05-24 09:30	400
B	1	2021-05-24 10:30	40
B	1	2021-05-24 11:30	4
C	1	2021-05-24 13:30	30
C	1	2021-05-24 14:30	300
C	2	2021-05-24 15:30	3

I'm trying to query the above table to display the following results

Product|ProductSubCode|MinYesterday|MaxYesterday|MinTwoDaysAgo|MaxToDaysAgo

ie For each product/sub code, select the min & max order amount for today and yesterday.

What I have so far is as follows;

SELECT distinct Product as masterID,ProductSubCode
(SELECT MIN(Order Amount) FROM TableName WHERE Product = masterID AND DateValue(OrderDateTime) >= DateAdd("d",-1,Date())) AS MinYesterday,
(SELECT MIN(Order Amount) FROM TableName WHERE Product = masterID AND DateValue(OrderDateTime) >= DateAdd("d",-1,Date())) AS MaxYesterday,
(SELECT MIN(Order Amount) FROM TableName WHERE Product = masterID AND DateValue(OrderDateTime) >= DateAdd("d",-2,Date())) AS MinTwoTodayAgo,
(SELECT MIN(Order Amount) FROM TableName WHERE Product = masterID AND DateValue(OrderDateTime) >= DateAdd("d",-2,Date())) AS MaxTwoDaysAgo
FROM TableName
GROUP BY Product, ProductSubCode

I get it, it's definitely wrong but I could really use some help here.

Answer 1

I think you are very close, changed it just a little bit:

1. It's better to avoid spaces in the column names, so use OrderAmount. If it's not possible to change a column name already, MIN([Order Amount]) will work instead of MIN(Order Amount) .

2. You have MIN in all the rows, whereas it should be MINs and MAXs.

3. I changed >= with = because you need a strict equation there

4. changed column alias masterID to table alias t1

SELECT distinct Product, ProductSubCode,
(SELECT MIN(OrderAmount) FROM TableName WHERE Product = t1.Product AND DateValue(OrderDateTime) = DateAdd("d",-1,Date())) AS MinYesterday,
(SELECT MAX(OrderAmount) FROM TableName WHERE Product = t1.Product  AND DateValue(OrderDateTime) = DateAdd("d",-1,Date())) AS MaxYesterday,
(SELECT MIN(OrderAmount) FROM TableName WHERE Product = t1.Product AND DateValue(OrderDateTime) = DateAdd("d",-2,Date())) AS MinTwoTodayAgo,
(SELECT MAX(OrderAmount) FROM TableName WHERE Product = t1.Product AND DateValue(OrderDateTime) = DateAdd("d",-2,Date())) AS MaxTwoDaysAgo
FROM TableName t1
GROUP BY Product, ProductSubCode

Answer 2

Try with these small adjustments using alias for the table in the subqueries:

SELECT 
    Product,
    ProductSubCode,
    (SELECT MIN(T1.[Order Amount]) FROM TableName AS T1
        WHERE T1.Product = TableName.Product AND DateValue(T1.OrderDateTime) = DateAdd("d",-1,Date())) AS MinYesterday,
    (SELECT MAX(T2.[Order Amount]) FROM TableName AS T2
        WHERE T2.Product = TableName.Product AND DateValue(T2.OrderDateTime) = DateAdd("d",-1,Date())) AS MaxYesterday,
    (SELECT MIN(T3.[Order Amount]) FROM TableName AS T3
        WHERE T3.Product = TableName.Product AND DateValue(T3.OrderDateTime) = DateAdd("d",-2,Date())) AS MinTwoTodayAgo,
    (SELECT MAX(T4.[Order Amount]) FROM TableName AS T4
        WHERE T4.Product = TableName.Product AND DateValue(T4.OrderDateTime) = DateAdd("d",-2,Date())) AS MaxTwoDaysAgo
FROM 
    TableName
GROUP BY 
    Product, 
    ProductSubCode

Answer 3

Use conditional aggregation!

SELECT Product as masterID, ProductSubCode,
       MIN(IIF(OrderDateTime >= DateAdd("d", -1, Date()) AND OrderDateTime < Date(), [Order Amount], NULL) as MinYesterday,
       MAX(IIF(OrderDateTime >= DateAdd("d", -1, Date()) AND OrderDateTime < Date(), [Order Amount], NULL) as MaxYesterday,
       MIN(IIF(OrderDateTime >= Date(), [Order Amount], NULL) as MinToday,
       MIN(IIF(OrderDateTime >= Date(), [Order Amount], NULL) as MaxToday
FROM TableName
WHERE OrderDateTime >= DateAdd("d", -1, Date())
GROUP BY Product, ProductSubCode;

In addition to being more concise, you should find that this has much, much, much better performance.

Note: This particular formulation assumes that you have no future order dates. It is easy enough to extend the WHERE clause to remove future order dates if that is an issue.