MYSQL: JOIN makes SUM double

Question

This should be really easy. Believe me, I\'ve been researching this for hours. My query:

SELECT not_piece.pid, part.name AS \'Part Name\', SUM(qty_left) AS \         


        

Answer 1

SELECT t.pid, p.name AS 'Part Name', t.InStock AS 'In Stock'
    FROM (SELECT pid, SUM(qty_left) AS InStock
              FROM not_piece
              GROUP BY pid) t
        INNER JOIN part p
            ON t.pid = p.pid

Answer 2

With your GROUP BY, try grouping by your primary key, pid:

SELECT not_piece.pid, part.name AS 'Part Name', SUM(qty_left) AS 'In Stock'
FROM not_piece 
JOIN part ON not_piece.pid = part.pid 
GROUP BY part.pid;