在sql连接中计算唯一记录

Question

Below query gives 400 record out of which 20 records is same based on UPC. In other words I want 20 distinct records based on UPC. How can I do it?

 select tc.ChainID,tc.UPC,tc.SupplierInvoiceNumber,pc.DateTimeCreated
     from #tmpCompareData tc
     left join ProductCatalog pc
    ON tc.ProductID=pc.ProductID 

Answer 1

Well, depending on what you are after, one solution would be to group by tc.UPC .

For example:

SELECT
    MIN(tc.ChainID),
    tc.UPC,
    MIN(tc.SupplierInvoiceNumber),
    MIN(pc.DateTimeCreated)
FROM #tmpCompareData tc
    LEFT JOIN ProductCatalog pc
ON tc.ProductID = pc.ProductID
GROUP BY tc.UPC

Note, that you need to apply aggregate functions ( MIN() , MAX() , etc.) to the other selected columns to tell SQL how you want to return that data.