Update README.md

README.md

@@ -138,7 +138,12 @@ db.orders.find( {"customer.id" : NumberLong( "1848533681975648" )}).pretty()
 ### requête 6
 
 ```js
-db.orders.aggregate([{$group : {_id :"$customer.id", Nombre_Commandes:{$sum:1}}}])
+db.orders.aggregate([
+  { $group: { 
+    _id: { id: "$customer.id", pseudo: "$customer.pseudo" }, 
+    Nombre_Commandes:{$sum:1} 
+  } }
+])
 ```