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Selecting from two tables: eliminating duplicates, but summing quantities

How can I query results from two tables? The tables consist of quantity and part columns. The query should return only one entry if the part duplicates, and at the same time sum up the quantity... and return those parts from both tables that don't duplicate. Is it possible?

Use a UNION ALL in a subquery to combine the two tables into one. Then select from that subquery using a GROUP BY. Here's an example:

select PartNo, sum(Quantity)
  from ( select PartNo, Quantity from Table_1
         union all 
         select PartNo, Quantity from Table_2 )
  group by PartNo;

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