sqlite – 从同一个表多个INNER JOIN

发布时间：2020-12-12 19:10:42 所属栏目：百科来源：网络整理

导读：我有一张金属桌子 MetalID integerMetalName textMetalCode text 物品表 ItemID integerItemName text...Metal1 int Ref.- metals.metalIDMetal2 int Ref.- metals.metalIDMetal3 int Ref.- metals.metalID 我试图选择三个MetalCodes SELECT m.MetalCode as

我有一张金属桌子

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.

您应该为表指定多个别名.你正在打电话给他们.

SELECT m1.MetalCode as 'Metal1',m2.MetalCode as 'Metal2',m3.MetalCode as 'Metal3'
FROM Item as k
INNER JOIN Metals AS m1 ON m1.metalID=k.metal1 
INNER JOIN Metals AS m2 ON m2.metalID=k.metal2
INNER JOIN Metals AS m3 ON m3.metalID=k.metal3
WHERE k.ItemID=?

（编辑：李大同）

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