a.
db.crimes.find({$or:[{"properties.method":"GUN"},{"properties.method":"KNIFE"}]}).count();
db.crimes.find({"properties.method":{$in:["GUN","KNIFE"]}}).count();
b.
db.crimes.find({$or:[{"properties.report_date":{$regex:/^2018-06/}},
			{"properties.report_date":{$regex:/^2018-07/}},
			{"properties.report_date":{$regex:/^2018-08/}}]
		}).count()
c.
db.crimes.find({},{_id:0,properties:1}).sort({"properties.report_date":1}).limit(3)
d.
db.crimes.update({"properties.neighborho":"Cluster 6"},{$set:{"properties.neighborho":"Cluster 666"}})

db.crimes.update({"properties.neighborho":"Cluster 6"},{$set:{"properties.neighborho":"Cluster 666"}},{multi=true})
e.
db.crimes.find({"properties.offense":{$regex:/THEFT/}}).count()
f.
db.crimes.aggregate([
	{ $project : { "properties.district": 1, _id: 0 } },
	{ $group: { _id: "$properties.district", total: { $sum:1 } } },
	{ $sort: {_id:1}}
	])
g.
db.crimes.aggregate([
	{ $project : { "properties.shift": 1, "properties.method": 1, _id: 0 } },
	{ $match: { "properties.method": "GUN" } },
	{ $group: { _id: "$properties.shift", total: { $sum:1 } } },
	{ $sort: {_id:1}}
	])
h.
db.crimes.aggregate([
	{ $project : { "properties.shift": 1, "properties.offense": 1, _id: 0 } },
	{ $match: { "properties.offense": "SEX ABUSE" } },
	{ $group: { _id: "$properties.shift", total: { $sum:1 } } },
	{ $sort: {_id:1}}
	])
i.
db.crimes.aggregate([
	{ $project : { "properties.offense": 1, _id: 0 } },
	{ $group: { _id: "$properties.offense", total: { $sum:1 } } },
	{ $sort: {_id:1}}
	])
j.
db.crimes.find({"properties.offense":{$in:["ROBBERY","ARSON"]}}).count()
k.
db.crimes.aggregate([
	{ $group: { _id: "$properties.district", totalcrimes: { $sum:1 } } },
	{ $group: { _id: null, avg: { $avg: '$totalcrimes' } } }
	])
l.
// 0%, c'est un piège : 
db.crimes.aggregate([
	{ $match: {"properties.report_date": {$regex:/^2018-08/}} },
	{ $group: { _id: "$properties.offense", total: { $sum:1 } } },
	])
m.
db.crimes.aggregate([
	{ $project : { "properties.district": 1, _id: 0 } },
	{ $group: { _id: "$properties.district", total: { $sum:1 } } },
	{ $sort: {"total":-1}},
	{ $limit: 1 }
	])
n.
db.crimes.deleteMany({"properties.offense": "ARSON"})
o.
// creer un index en 1er lieu
db.crimes.createIndex({"geometry":"2dsphere"})
// puis la requête
db.crimes.find({
   "geometry": {
	$near: {
		$geometry: {
		type: "Point" ,
		coordinates: [ -77.03652979999998, 38.8976763 ]
		},
		$maxDistance: 500
	}}
}).count()
p.
// distinct
db.crimes.distinct("properties.offense",{
   "geometry": {
	$near: {
		$geometry: {
		type: "Point" ,
		coordinates: [ -77.03652979999998, 38.8976763 ]
		},
		$maxDistance: 500
	}}
},{"properties.offense":1, "_id":0})
q.
// Portez attention au champ result...
db.crimes.aggregate([
         {
             $geoNear: {
                near: { type: "Point", coordinates: [ -77.009003, 38.889931 ] },
		key: "geometry",
                distanceField: "result.distance",
                includeLocs: "result.location",
                num: 10,
                spherical: true
             }
           }
])