1."$inc"的使用
主要用来增加数值，比如网站的访问量，点击量，流量等
1 db.games.insert({game:"pinball",user:"joe"})
2 db.games.find()
3 db.games.update({"game":"pinball","user":"joe"},{"$inc":{"score":50}})
4 db.games.update({"game":"pinball","user":"joe"},{"$inc":{"score":10000}})
运行结果分别为
1 /* 1 */
2 {
3 "_id" : ObjectId("575a37da8fd26400d774e00a"),
4 "game" : "pinball",
5 "user" : "joe",
6 "score" : 10150.0
7 }
db.games.update({"game":"pinball","user":"joe"},{"$inc":{"score":50}})
1 /* 1 */
2 {
3 "_id" : ObjectId("575a37da8fd26400d774e00a"),
4 "game" : "pinball",
5 "user" : "joe",
6 "score" : 10200.0
7 }