从mySQL中检索另一个数据以获取项目建议

Question

Basically I am currently doing a recommendation system for my website

I have 4 tables in mySQL database:

Users

• userID
• username
• password
• userLevel

category

• categoryID
• type

item

• itemID
• name
• price
• quantity
• categoryID
• description

transaction

• transactionID
• categoryID
• itemID
• userID

So this is how it I want it works,

userID 1(Kyle) bought Laptop(ItemID 1), Mouse(ItemID 2), and Battery(ItemID 4)

userID 2(Steven) bought Laptop(itemID 1)

userID 3(Jonathan) bought Mouse(ItemID 2), Battery(ItemId 4), and Mousepad(ItemID 3)

I want the system to recommend itemID 2(Mouse), itemID4(Battery), and ItemID 3 (Mousepad) to userID 2(Steven)

• The transaction table will record any transaction made.

Any helps given are highly appreciated. Thanks

Answer 1

What the query does is get the All UserID's which bought the ItemID=2 . And then Get the ItemID bough by those users. and then apply the filter to remove the ItemId =2 from the result.Try this.

Select distinct ItemID 
FROM transaction 
where UserID IN (Select userID FROM Transaction where itemID = 2 ) 
AND ItemID <> 2

Answer 2

Like this

SELECT
    i.itemID,
    i.name,
    u.username
FROM transaction
    INNER JOIN user u ON (u.userID = t.userID)
WHERE u.userID = 2

Then you have to work with your language to convert the result to a readable line.

Else you'll have to look for "PIVOT" to convert multiple bought items (multiple lines) to a single line.

An other solution would be to use a transaction with mssql, allowing to parse the results and return a single line.