MySQL Query, (access mainquery from subquery) - mysql

Question

I have a problem that I need a WHERE clause in a subquery that depends on the results of the main Query, otherwise my results would be wrong and the query takes too long / is not executeable.
The circumstances that I need this query to create a view which I need for a search server support the problem that I cannot split this into two queries, nor process it with a script dynamically.
The problem occurs with the following query:
SELECT `s`.`id` AS `seminar_id`, (SUM( `sub`.`seminar_rate` ) / COUNT( `sub`.`seminar_id` )) AS `total_rate`
FROM
(
SELECT (SUM( value ) / COUNT( * )) AS `seminar_rate` , `r`.`seminar_id`
FROM `rating` r
INNER JOIN `rating_item` ri ON `r`.`id` = `ri`.`rating_id`
WHERE `r`.`seminar_id` = `s`.`id`/* <- Here is my problem, this is inacessible */
GROUP BY `r`.`seminar_id`
) AS sub,
`seminar` s
INNER JOIN `date` d
ON `s`.`id` = `d`.`seminar_id`
INNER JOIN `date_unit` du
ON `d`.`id` = `du`.`date_id`
LEFT JOIN `seminar_subject` su
ON `s`.`id` = `su`.`seminar_id`
LEFT JOIN `subject` suj
ON `su`.`subject_id` = `suj`.`id`
INNER JOIN `user` u
ON `s`.`user_id` = `u`.`id`
INNER JOIN `company` c
ON `u`.`company_id` = `c`.`id`
GROUP BY `du`.`date_id`, `sub`.`seminar_id`
This query should calculate a total rate out of ratings for each Seminar.
However my ratings are stored in my "rating" table and should be processed live.
(Sidenote: If you wonder about all the joins: This query has alooot more SELECT'ed fields, I just removed them because they are not nesessary to solve the problem and to make the query look less complicated [I know it still is >.>]...)
The reason is that I want this results to be sortable by my search engine later depending
on the users sort parameters, thatswhy I need it inside this query.
The problem itself is pretty obvious:
ERROR 1054 (42S22): Unknown column 's.id' in 'where clause'
The subselect doesnt know about the results of the main query, is there a solution to bypass this?
Could someone give me a hint to get this working?
Thanks in advance.

Answer 1

Using your subquery in the JOIN you can eliminate the WHERE clause and achieve nearly the same result. Here is your modified query. Hope this solves your problem.
SELECT `s`.`id` AS `seminar_id`, (SUM( `sub`.`seminar_rate` ) / COUNT( `sub`.`seminar_id` )) AS `total_rate`
FROM `seminar` s
INNER JOIN
(
SELECT (SUM( value ) / COUNT( * )) AS `seminar_rate` , `r`.`seminar_id`
FROM `rating` r
INNER JOIN `rating_item` ri ON `r`.`id` = `ri`.`rating_id`
/*WHERE `r`.`seminar_id` = `s`.`id` <- Here is my problem, this is inacessible */
GROUP BY `r`.`seminar_id`
) AS sub ON s.id = sub.`seminar_id`
INNER JOIN `date` d
ON `s`.`id` = `d`.`seminar_id`
INNER JOIN `date_unit` du
ON `d`.`id` = `du`.`date_id`
LEFT JOIN `seminar_subject` su
ON `s`.`id` = `su`.`seminar_id`
LEFT JOIN `subject` suj
ON `su`.`subject_id` = `suj`.`id`
INNER JOIN `user` u
ON `s`.`user_id` = `u`.`id`
INNER JOIN `company` c
ON `u`.`company_id` = `c`.`id`
GROUP BY `du`.`date_id`, `sub`.`seminar_id`