连接2个表，并根据其关联ID重复显示同一列

Question

Hi i am not sure how to put this in a brief sentences, but i have DB table like the following

User Table

• user_id
• username
• and so on...

Item

• item_id
• item_name

Item_Equipped

• equipped_id head (FK to item_id)
• hand (FK to item_id)
• user_id (FK to user_id IN User Table)

I would like to generate a query that will display like the following format

user_id | head | head_item_name | hand | hand_item_name | ...

So far i only able to do this:

SELECT user.user_id, user.username,
        equipments.head, equipments.head_acc,
        equipments.hand,
        equipments.acc, equipments.body
FROM gw_member_equipped AS equipments
LEFT JOIN gw_member AS user ON user.memberid = equipments.member_id

Which (i have to be brutally honest) doesn't do anything much.

I tried to perform INNER JOIN between item and item_equipped however i am unable to get individual name for each item (based on its item ID)

Answer 1

you need to join ITEM table two times with ITEM_EQUIPPED table.

you can use below query for your desired output column shown in question..

SELECT USER.User_Id,
       Item_Equipped.Head,
       Item_Heads.Item_Id Head_Item_Id, -- if you want you can remove this column
       Item_Heads.Item_Name Head_Item_Name,       
       Item_Equipped.Hand,
       Item_Hands.Item_Id Hand_Item_Id,  -- and this column also as these columns are same as their previous select columns
       Item_Hands.Item_Name Hand_Item_Name
  FROM USER, Item Item_Heads, Item Item_Hands, Item_Equipped
 WHERE USER.User_Id = Item_Equipped.User_Id
   AND Item_Heads.Item_Id = Item_Equipped.Head
   AND Item_Hands.Item_Id = Item_Equipped.Hand