mongo数据更新

> db.stu.find({},{"_id":0})
{ "name" : "张三", "sex" : "男", "age" : 18, "score" : 70, "address" : "河南" }
{ "name" : "李四", "sex" : "女", "age" : 20, "score" : 60, "address" : "山东" }
{ "name" : "王五", "sex" : "男", "age" : 17, "score" : 44, "address" : "江苏" }
{ "name" : "赵六", "sex" : "男", "age" : 21, "score" : 80, "address" : "山东" }
{ "name" : "孙七", "sex" : "女", "age" : 23, "score" : 50, "address" : "湖北" }
{ "name" : "tom", "sex" : "男", "age" : 24, "score" : 20, "address" : "海南" }
{ "name" : "lucy", "sex" : "女", "age" : 21, "score" : 62, "address" : "浙江" }
{ "name" : "jack", "sex" : "男", "age" : 20, "score" : 90, "address" : "美国" }
{ "name" : "smith", "sex" : "男", "age" : 19, "score" : 88, "address" : "美国" }

#1.把年龄<20岁的分数更新为60
db.stu.find({"age":{"$lt":20}},{"_id":0});
{ "name" : "张三", "sex" : "男", "age" : 18, "score" : 70, "address" : "河南" }
{ "name" : "王五", "sex" : "男", "age" : 17, "score" : 44, "address" : "江苏" }
{ "name" : "smith", "sex" : "男", "age" : 19, "score" : 88, "address" : "美国" }


db.stu.update({"age":{"$lt":20}},{"$set":{"score":100}},false,false);
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
#只修改了一个
db.stu.find({"age":{"$lt":20}},{"_id":0});
{ "name" : "张三", "sex" : "男", "age" : 18, "score" : 100, "address" : "河南" }
{ "name" : "王五", "sex" : "男", "age" : 17, "score" : 44, "address" : "江苏" }
{ "name" : "smith", "sex" : "男", "age" : 19, "score" : 88, "address" : "美国" }
#全部修改
db.stu.update({"age":{"$lt":20}},{"$set":{"score":100}},false,true);
db.stu.find({"age":{"$lt":20}},{"_id":0});
{ "name" : "张三", "sex" : "男", "age" : 18, "score" : 100, "address" : "河南" }
{ "name" : "王五", "sex" : "男", "age" : 17, "score" : 100, "address" : "江苏" }
{ "name" : "smith", "sex" : "男", "age" : 19, "score" : 100, "address" : "美国" }

save()

db.stu.save({"_id" : ObjectId("592cc2e00be561e9e879bcb5"),"name":‘张三三‘});
只能根据_id更新