MetalID    integer
MetalName  text
MetalCode  text

物品表

ItemID     integer
ItemName   text
...
Metal1     int Ref.-> Metals.MetalID
Metal2     int Ref.-> Metals.MetalID
Metal3     int Ref.-> Metals.MetalID

我试图选择三个MetalCodes

SELECT m.MetalCode as 'Metal1',m.MetalCode as 'Metal2',m.MetalCode as 'Metal3'
FROM Item as k
INNER JOIN Metals AS m ON m.MetalID=k.Metal1 
INNER JOIN Metals AS m ON m.MetalID=k.Metal2
INNER JOIN Metals AS m ON m.MetalID=k.Metal3
WHERE k.ItemID=?

看起来我完全错了.请帮忙.