I don't know how to perform the the following case.
I have the sales info in a table:
Number of Bill (key) Inteal number (key) Client Date (month-year) Product group Product Quantities on the bill Total price of the line Sales man
I need to joint this sales tables with the aual forecast sales table that is the next one:
Date (key) Group product(key) Sales man (key) Total
In each tables the combination of the key is the primary key. I need to add in the sales tables the forecast. For this I need to add the sales of the forecast in th real sale only on the first match of date, group product and sales man, so the total of forecast sales don't get bigger than it is (a sales man can sell the same group product, to the same client, in the same day on multiple times).