score是已经创建的集合
db.score.insert({"_id": 103, "subject": "语文", "score": 55, "stuId": 1002})
db.score.save({"_id": 102, "subject": "数学", "score": 80, "stuId": 1002}) =>save操作的_id如果存在,则做更新
db.score.insertMany({"_id": 103, "subject": "语文", "score": 55, "stuId": 1002},
{"_id": 104, "subject": "语文", "score": 55, "stuId": 1003})
db.score.insertOne({"_id": 105, "subject": "语文", "score": 55, "stuId": 1004})