Joindre des tables et agréger des données dans MySQL?

Question

J'ai 2 tables. Les membres et leurs projets. J'ai besoin d'extraire tous les utilisateurs, avec le nombre de leurs projets, triés par le nombre de projets.

Tableau: users:

id | username | email | password | reg_date 

Tableau: projects:

id | title | descr | autor 

Pour le rejoindre:

projects.autor = users.id 

Answer 1

SELECT 
    users.id, 
    users.username, 
    COUNT(projects.id) AS `num_projects` 
FROM 
    users 
LEFT OUTER JOIN 
    projects 
ON 
    projects.autor = users.id 
GROUP BY 
    users.id 
ORDER BY 
    num_projects DESC 

Answer 2

SELECT u.id AS id, u.username AS username, u.email AS email, u.password AS password, u.reg_date AS reg_date, COUNT(p.id) AS projects_count 
FROM users u 
LEFT OUTER JOIN projects p ON p.autor = u.id 
GROUP BY u.id 
ORDER BY projects_count DESC