使用Apache在Linux上的MySQL数据库中的三个表上进行内部，外部或完全联接

Question

I want to have some help creating my query to get information from three different tables sharing information in common. My first table is:

auctions
id title description user_id(who posted it)

My second table is:

bids
id user_id bid auction_id owner_id

My third table is:

users
id username X XX XXX XXXX 

...and my SQL is as follows however it's not returning any results:

SELECT auction_bids.user_id AS applicant, auction_bids.*, auctions.title FROM auction_bids, auctions
        WHERE auctions.user_id=".$_SESSION['userid']."  
        INNER JOIN users ON auction_bids.user_id = users.id 
        WHERE auction_bids.owner_id = ".$_SESSION['userid']."

What I need is to capture the auction's title, username who bidded on the auction and the bid. the auction has to have a bid and posted by the user who owns the $_SESSION['userid']. Any help is appreciated.

Answer 1

You have two different 'where' statements, which may just need combining;

SELECT auction_bids.user_id AS applicant, auction_bids.*, auctions.title FROM auction_bids, auctions INNER JOIN users ON auction_bids.user_id = users.id WHERE auction_bids.owner_id = ".$_SESSION['userid']." AND auctions.user_id=".$_SESSION['userid']."

However, I'm not sure this is really what you want, as it will return only records where the specific user both 'owns' the item AND has bidded on it (both based on the userid session), rather than displaying all records from different people who have bidded on an item 'owned' by the user.

Something like: ? SELECT auction_bids.user_id AS applicant, auction_bids.*, auctions.title FROM auction_bids, auctions INNER JOIN users ON auction_bids.user_id = users.id, WHERE auction.owner_id = ".$_SESSION['userid']."

Hope this points you in the right direction!

Answer 2

you have 2 where clauses, that is incorrect. I have revised your query based on your requirements.

SELECT auction_bids.user_id AS applicant, auction_bids.*, auctions.title 
FROM auction_bids, auctions
        INNER JOIN users ON auction_bids.owner_id = users.id 
        WHERE auction_bids.owner_id = ".$_SESSION['userid']."
        AND auctions.user_id=auctions_bids.owner_id