-- Query 21

SELECT
    serveur.villeserveur as 'ville',
    COUNT(serveur.numserveur) as 'nb serveurs'
FROM
    serveur
GROUP BY serveur.villeserveur;

/* == RESULT ==
"Ville","Nb Serveurs"
"BAVILLIERS",1
"BELFORT",2
"DELLE",1
"DIJON",1
*/