如何在SELECT查询中包含“订单”或“索引”列？

Question

I'm using Access SQL . I want to add a column to my query that acts like a row number for each record, but because I'm using an aggregate function, the results have not ids themselves. Is there any function that generate some row numbers for this ? even like Autonumber or index or just the order . So my dummy SQL syntax is like:

SELECT [wanted autonumber column], product,Sum(amount) FROM Invoices_Items GROUP BY product

I guessed maybe it would be good if I create a temporary table for this query with an autonumber column but I don't know how to that.

Answer 1

If you save the GROUP BY SQL as a named query in Access, you can use that as the data source for another SELECT statement which uses a correlated subquery to generate a row number.

So with this SQL saved as qryInvoices_Items1 ...

SELECT i.product, Sum(i.amount) AS SumOfamount
FROM Invoices_Items AS i
GROUP BY i.product;

This query will add a dynamic row number --- the row number for a given product can be different from one run to the next if the underlying Invoices_Items data changes.

SELECT
    (
        SELECT Count(*)
        FROM qryInvoices_Items1 AS q2
        WHERE q2.product <= q1.product
    ) AS row_number,
    q1.product,
    q1.SumOfamount
FROM qryInvoices_Items1 AS q1;

I tested that SQL in Access 2007, and it returns the result I think you're looking for. However, if I'm wrong about that point, please include Invoices_Items sample data in your question (as text, not a screen capture image) and show us the output you want based on that sample data.

Note a correlated subquery requires the db engine run that subquery separately for each row of the parent query's result set. That would be a big performance challenge with a huge data set. However, if your data set is small enough, the perform impact could be tolerable, or maybe not even noticeable.