MySQL dove clausola e ordinamento da avg () come una query secondaria

Question

Sebbene sia possibile raggruppare e ordinare in base a una query secondaria con alias, non posso utilizzare l'alias in una clausola where. Devo usare un join invece?

Opere:

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

Errore (" colonna sconosciuta 'avg_rating' nella clausola where "):

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

Potresti riuscire a farlo con una clausola HAVING anziché con WHERE

Sintassi

Answer 2

Vorrei fare un join e groupby Ad esempio,

SELECT entries.*, AVG(value)
FROM entries INNER JOIN ratings ON entries.id = ratings.entry_id 
GROUP BY entries.*
HAVING AVG(value) < '4.5000' 
ORDER BY AVG(value)

Solo codice psuedo, ti consiglio anche di limitare le colonne delle voci esattamente a ciò che ti serve.

Potresti riuscire a cavartela con l'alias come:

SELECT entries.*, AVG(value) as avg_value
FROM entries INNER JOIN ratings ON entries.id = ratings.entry_id 
GROUP BY entries.*
HAVING avg_value < '4.5000' 
ORDER BY avg_value