SQL LEFT JOIN with possible join condition duplicate match - mysql

Question

Here is my query so far:
SELECT
b.cs_bidding_id, b.cs_bidding_user_id,
floor(AVG(u.cs_rating)) AS cs_user_rating
FROM cs_biddings b LEFT JOIN
cs_user_ratings u ON u.cs_user_rated_id = b.cs_bidding_user_id
I would like to get the avg rating of the user's per bidding post.
However this does not work for multiple biddings because whenever the join condition is satisfied, it wont let me fetch other avg rating for other biddings that shares the same bidding_user_id
desired result:
Unsummarized Query:
SELECT
b.cs_bidding_id,
b.cs_bidding_title,
b.cs_bidding_details,
b.cs_bidding_user_id,
b.cs_bidding_permalink,
b.cs_bidding_added,
b.cs_bidding_picture,
b.cs_bidding_status,
b.cs_bidding_location,
floor(AVG(u.cs_rating)) AS cs_owner_rating
FROM cs_biddings b LEFT JOIN
cs_user_ratings u ON u.cs_user_rated_id = b.cs_bidding_user_id

Answer 1

Your query is malformed. It is an aggregation query (because of the AVG()) but the SELECT columns are inconsistent with the aggregation columns (well, there are none of those).
Fixing the group by might fix your problem:
SELECT b.cs_bidding_id, b.cs_bidding_user_id,
floor(AVG(u.cs_rating)) AS cs_user_rating
FROM cs_biddings b LEFT JOIN
cs_user_ratings u
ON u.cs_user_rated_id = b.cs_bidding_user_id
GROUP BY b.cs_bidding_id, b.cs_bidding_user_id;
I'm not sure if you want both columns in the GROUP BY (and the result set). However, without sample data and desired results, it is unclear what you actually intend.