Him I'm building a kind of auction application except instead of buying
and selling items, users can swap them with each other. I am struggling
with the syntax for the queries.
I have tables for items, auctions, bids and users set up as follows.
Bid has many items as I would like the user to be able to offer more
than one item in their bid, for example one user trades 3 items with
another user for 1 more expensive item.
I'm trying to find all auctions that the current user has placed a bid
on (I would like to display the item title of the auction).
At the moment I can only work out how to get the auction ID like so...
<% for bid in @bids %>
<tr>
<td><%= bid.auction_id %></td>
</tr>
Finally, how can I make the search unique? IE if the user has placed
multiple bids on one auctions, how can I make that auction appear only
once in the results?
I think I could work it out ok in SQL, but I have found it difficult to
find many resouces on ruby.
Ah, I didn't know about find_by_sql, thanks.
I think I have the query right now, but I'm still having a few problems
putting with the ruby syntax. Can anyone see the problem here? Thanks.
@bids = Auction.find_by_sql [SELECT * FROM auctions WHERE id = (SELECT
auction_id FROM bids WHERE user_id = ?, session[:user][:id])]
OK, I've got it to work, but only if I put in a literal value..
eg,
@auctions = Auction.find_by_sql("SELECT * FROM auctions WHERE id =
(SELECT auction_id FROM bids WHERE user_id = 2 )")
However, the following returns no results...
@sid = session[:user][:id] (@sid is 2)
@auctions = Auction.find_by_sql("SELECT * FROM auctions WHERE id =
(SELECT auction_id FROM bids WHERE user_id = @sid )")
Hmm, I'd have expected that it would be better couched as:
Assuming:
class Bid
belongs_to :user
belongs_to :auction
end
class Auction
has_many :bids
end
class User
has_many :bids
has_many :auctions, :through => :bids
end
user = User.find_by_id session[:user][:id]
@auctions = user.auctions
or at the very least:
@auctions = Auction.find_by_sql("SELECT auctions.* FROM auctions WHERE auctions.id IN (SELECT bids.auction_id FROM bids WHERE bids.user_id = #{@sid})")
Perhaps I answered too narrow a question. The OP wondered why his query was not returning the expected result set and it was because he hadn't used the string interpolation syntax (near as I can tell). As you point out, there is a Rails way to solve the problem better.