--SOUS REQUETES EN SELECT

SELECT nom, (SELECT AVG(salaire) FROM Employes) AS salaire_moyen FROM Employes.

--SOUS REQUETES EN FROM

SELECT dept, moyenne FROM (SELECT dep AS dept, AVG(salaire) AS moyenne FROM Employes GROUP BY dep) AS dep_stats;

--SOUS REQUETES WHERE

SELECT nom FROM employes WHERE salaire > (SELECT AVG(salaire) FROM Employes);