Counting checked items in database - vb.net

Question

In my database I have table with multiple "yes/no" rows on which I would like to run some selection check if they are selected or not.
ITEM ORDERED ORDER_ID
item1 true 1
item2 false 1
item3 true 2
item4 true 3
item5 true 4
item6 true 4
In datagridview in my code I will like to achieve this.
ORDER STATUS
1 not ordered
2 ordered
3 ordered
4 ordered
In my code I will like to go through all orders and check if status of ordered items on that order is true. If all items on some order have status true, then i will like to set another flag that I have in ORDER table to true(ordered). Which is the most elegant way to solve this problem? If you have some example of this like problem I will really appreciate it. Thanks in advance.

Answer 1

It appears STATUS means whether all rows for that ORDER_ID have ORDERED = True. If that is correct, I think you can get what you need with an Access aggregate (GROUP BY) query.
True is stored as -1 and False is stored as 0. So if the maximum ORDERED value for any ORDER_ID is 0, you know there is at least one item for that order which has not yet been ordered. If the maximum is -1, then all items have been ordered.
Start with a query to determine Max(ORDERED) for each ORDER_ID.
SELECT y.ORDER_ID, Max(y.ORDERED) AS MaxOfORDERED
FROM YourTable AS y
GROUP BY y.ORDER_ID;
Once you have that working, use it as a subquery in another with an IIf expression to transform MaxOfORDERED to the STATUS text you want.
SELECT
sub.ORDER_ID,
IIf(sub.MaxOfORDERED = 0, 'not ordered', 'ordered') AS STATUS
FROM
(
SELECT y.ORDER_ID, Max(y.ORDERED) AS MaxOfORDERED
FROM YourTable21030926a AS y
GROUP BY y.ORDER_ID
) AS sub
ORDER BY sub.ORDER_ID;