Question

Although I can group and order by on an aliased sub query, I can’t use the alias in a where clause. Do I need to use a join instead?

Works:

SELECT entries.*, 
    (SELECT avg(value) 
    FROM `ratings`
    WHERE ratings.entry_id = entries.id) as avg_rating
FROM `entries` 
ORDER BY avg_rating DESC

Fails (“unknown column ‘avg_rating’ in where clause”):

SELECT entries.*, 
    (SELECT avg(value) 
    FROM `ratings` 
    WHERE ratings.entry_id = entries.id) as avg_rating 
FROM `entries` 
WHERE avg_rating < '4.5000' ORDER BY avg_rating DESC

Answer 1

You may be able to do this with a HAVING clause instead of a WHERE

Syntax