MySQL 一对多，只从多表中提取选定的记录

Question

I am quite new at SQL statements and I have never been very good at joins etc. I am having a problem working out how to do the following:

I have 2 tables, one called MUSIC, one called REVIEWS. The two tables link on a field called uid - records in MUSIC are unique, but there may be many reviews for each MUSIC record.

REVIEWS has a field called thumbsup, which is set to value 1 if a user gives a MUSIC the thumbs up. Otherwise, the field is zero. There may be many thumbsup in REVIEWS, one thumbsup, or no thumbsup.

I am trying to display a list of records in MUSIC, and if there is a corresponding REVIEW record that contains a thumbsup value of 1 - just one record in REVIEWS will do it - then to display an icon on the list page.

I have had a good look around various similar questions but nothing quite like this comes up. I have tried doctoring around similar kinds of joins, but frankly how it all works is beyond me. Sorry for being an idiot.

By way of evidence that I have at least had a go, so far I have come up with this based on another post:

SELECT m.*, r.thumbsup 
FROM (SELECT MAX(thumbsup) uid FROM reviews GROUP By uid) maxThumbs 
INNER JOIN reviews r ON maxThumbs.uid = reviews.uid 
INNER JOIN music m ON music.uid = reviews.uid  

Needless to say it doesn't work:(

If anyone could help me out here with the right query structure I would be extremely grateful.

Many thanks

Ted.

Answer 1

select DISTINCT m.* from music m INNER JOIN reviews r on m.uid = r.uid where r.thumbsup > 0 

Answer 2

How about something like this:

SELECT m.*, IFNULL((SELECT 1 FROM reviews r WHERE r.thumbsup > 0 AND m.uid = r.uid LIMIT 1),0) has_review 
FROM music m

Answer 3

SELECT m.* 
FROM music m
INNER JOIN 
  (SELECT DISTINCT reviews.uid WHERE review.thumbsup > 0) r ON (r.uid = m.uid)

Answer 4

SELECT DISTINCT m.*, r.thumbsup
FROM music m LEFT JOIN reviews r 
ON (m.uid = r.uid AND r.thumbsup=1);

Will return music records with no reviews, no positive reviews, mixed reviews, postivie only reviews (with any positive reviews indicated)