Question

My query is:

SELECT business.name, AVG(rating.value) as total  
FROM business   
INNER JOIN rating   
   ON business.id = rating.business_id   
INNER JOIN directory   
   ON business.id = directory.item_id  
WHERE directory.directory_id = 13    
   AND directory.type = 'business'   
   AND rating.rating_id = '1'   
GROUP BY business.id   
ORDER BY total DESC  

My problem is that I want to include any businesses even if they do not have any ratings associated with them?

Answer 1

You need to use LEFT JOIN instead of INNER JOIN:

SELECT business.name, AVG(rating.value) as total  
FROM business   
INNER JOIN directory   
   ON business.id = directory.item_id  
LEFT JOIN rating   
   ON business.id = rating.business_id AND rating.rating_id = '1'
WHERE directory.directory_id = 13    
   AND directory.type = 'business'   
GROUP BY business.id   
ORDER BY total DESC

If there are no ratings, total will be NULL.
You can deal with this in MySQL (if you want) like this:

IFNULL(AVG(rating.value), 'No ratings') as total 

Also note you need to move the rating.rating_id = '1' to the JOIN conditions.