MongoDB——增删改查

文档结构：

{
    "_id": ObjectId("5d5e5de597eb2f0b70005d1a"),
    "userId": 1234,
    "word_records": [
        {
            "word": "helloo",
            "from": "en",
            "to": "hi",
            "update_time": 1245748,
            "create_time": 235689
        },
        {
            "word": "xx",
            "from": "en",
            "to": "hi",
            "update_time": 1245748,
            "create_time": 235689
        }
    ]
}

一个用户想增加一个单词：

db.getCollection("collect_record").update({'userId':1234},{$addToSet:{word_records:{'word':'update2','to':'en','from':'hi'}}})

一个用户想删除一个单词：

db.getCollection("collect_record").update({"userId":123},{"$pull":{"word_records":{"word":"hello"}}})

分页查询某个用户的单词：

db.getCollection("collect_record").findOne({'userId':123},{'word_records':{$slice:[0,2]}})