mongodb查询练习

准备数据的脚本

本文参考http://www.jb51.net/article/48217.htm，在此基础上整理成自己的一套mongodb练习文档

db.users.drop();
var user1 = {
    "name" : "xiaobu",
    "country" : "china",
    "comments" : 
        [ 
            {
                "userId" : "001",
                "content" : "评论1",
                "commentTime" : "2018-04-22 22:50:48.39"
            }, 
            {
                "userId" : "002",
                "content" : "评论2",
                "commentTime" : "2018-04-22 22:51:48.39"
            }, 
            {
                "userId" : "003",
                "content" : "评论3",
                "commentTime" : "2018-04-22 22:52:48.39"
            }, 
            {
                "userId" : "004",
                "content" : "评论4",
                "commentTime" : "2018-04-22 22:53:48.39"
            }, 
            {
                "userId" : "005",
                "content" : "评论5",
                "commentTime" : "2018-04-22 22:54:48.39"
            }, 
            {
                "userId" : "006",
                "content" : "评论6",
                "commentTime" : "2018-04-22 22:55:48.39"
            }, 
            {
                "userId" : "007",
                "content" : "评论7",
                "commentTime" : "2018-04-22 22:56:48.39"
            }, 
            {
                "userId" : "008",
                "content" : "评论8",
                "commentTime" : "2018-04-22 22:57:48.39"
            }, 
            {
                "userId" : "009",
                "content" : "评论9",
                "commentTime" : "2018-04-22 22:58:48.39"
            }
        ],
    "address" : {
        "aCode" : "001",
        "aName" : "长沙"
    },
    "favorites" : {
        "books" : [ 
            "西游记", 
            "红楼梦", 
            "三国演义", 
            "水浒传"
        ],
        "cites" : [ 
            "韶关", 
            "深圳", 
            "佛山"
        ],
        "fruits" : [ 
            "apple", 
            "banana", 
            "watermelon"
        ]
    },
    "age" : 26.0,
    "salary" : NumberDecimal("18889.09"),
    "height" : 1.7
};

var user2 = {
    "name" : "juyi",
    "country" : "china",
    "comments" : [
     {
                "userId" : "101",
                "content" : "评论101",
                "commentTime" : "2018-04-22 22:50:48.39"
            }, 
            {
                "userId" : "102",
                "content" : "评论102",
                "commentTime" : "2018-04-22 22:51:48.39"
            }
    ],
    "address" : {
        "aCode" : "002",
        "aName" : "韶关"
    },
    "favorites" : {
        "movies" : [ 
            "肖生克的救赎", 
            "阿甘正传", 
            "头号玩家"
        ],
        "cites" : [ 
            "衡阳", 
            "南宁", 
            "上海", 
            "深圳"
        ],
        "fruits" : [ 
            "durian", 
            "watermelon"
        ]
    },
    "age" : 25.0,
    "salary" : NumberDecimal("18889.09"),
    "height" : 1.5
};
var user3 = {
    "name" : "tom",
    "country" : "USA",
    "comments":{
                  "$ref" : "comments",
                  "$id" : ObjectId("5ae20a927aec117179c68468"),
                  "$db" : "test"
        },
    "address" : {
        "aCode" : "003",
        "aName" : "纽约"
    },
    "favorites" : {
        "movies" : [ 
            "头号玩家", 
            "肖生克的救赎", 
            "阿甘正传"
        ],
        "cites" : [ 
            "旧金山", 
            "纽约"
        ],
        "fruits" : [ 
            "durian", 
            "watermelon"
        ]
    },
    "age" : 18.0,
    "height" : 1.88
};
var user4 = {
    "name" : "tom",
    "country" : "USA",
    "address" : {
        "aCode" : "001",
        "aName" : "纽约"
    },
    "favorites" : {
        "movies" : [ 
            "头号玩家", 
            "肖生克的救赎", 
            "阿甘正传"
        ],
        "cites" : [ 
            "旧金山", 
            "纽约"
        ],
        "fruits" : [ 
            "durian", 
            "watermelon"
        ]
    },
    "age" : 18.0,
    "height" : 1.88
};
var user5 = {
    "name" : "tony",
    "country" : "USA",
    "address" : {
        "aCode" : "004",
        "aName" : "洛杉矶"
    },
    "favorites" : {
        "books" : [ 
            "权利的游戏", 
            "飘", 
            "谁动了我的奶酪"
        ],
        "cites" : [ 
            "芝加哥", 
            "洛杉矶"
        ],
        "fruits" : [ 
            "durian", 
            "watermelon"
        ]
    },
    "age" : 28.0,
    "height" : 1.79
};
var user6 = {
    "name" : "xiaoxiaobu",
    "country" : "USA",
    "address" : {
        "aCode" : "005",
        "aName" : "费城"
    },
    "favorites" : {
        "books" : [ 
            "权利的游戏", 
            "教父"
        ],
        "cites" : [ 
            "芝加哥", 
            "芝加哥", 
            "洛杉矶"
        ],
        "fruits" : [ 
            "durian", 
            "watermelon"
        ]
    },
    "age" : 20.0,
    "height" : 1.71
};
var user7 = {
    "name" : "lily",
    "country" : "USA",
    "address" : {
        "aCode" : "001",
        "aName" : "费城"
    },
    "favorites" : {
        "books" : [ 
            "权利的游戏", 
            "飘", 
            "谁动了我的奶酪"
        ],
        "cites" : [ 
            "芝加哥", 
            "芝加哥", 
            "洛杉矶"
        ],
        "fruits" : [ 
            "durian", 
            "watermelon"
        ]
    },
    "age" : 20.0,
    "height" : 1.71
};
var user8 = {
    "name" : "xiaoxiao",
    "country" : "USA",
    "address" : {
        "aCode" : "001",
        "aName" : "费城"
    },
    "favorites" : {
        "books" : [ 
            "权利的游戏", 
            "飘", 
            "谁动了我的奶酪"
        ],
        "cites" : [ 
            "芝加哥", 
            "芝加哥", 
            "洛杉矶"
        ],
        "fruits" : [ 
            "durian", 
            "watermelon"
        ]
    },
    "age" : 21.0,
    "height" : 1.71
};

db.users.insert(user1);
db.users.insert(user2);
db.users.insert(user3);
db.users.insert(user4);
db.users.insert(user5);
db.users.insert(user6);
db.users.insert(user7);
db.users.insert(user8);

内容评论表

var comment1 = {
    "_id" : ObjectId("5ae20a927aec117179c68468"),
    "lists":
    [ 
            {
                "userId" : "tom1",
                "content" : "tom评论1",
                "commentTime" : "2018-04-22 22:50:48.39"
            }, 
            {
                "userId" : "tom2",
                "content" : "tom评论2",
                "commentTime" : "2018-04-22 22:51:48.39"
            }, 
            {
                "userId" : "tom3",
                "content" : "tom评论3",
                "commentTime" : "2018-04-22 22:52:48.39"
            }
    ]
};
var comment2 = {
"_id" : ObjectId("5ae20a947aec117179c68469"),
 "lists":
    [ 
            {
                "userId" : "tony1",
                "content" : "tony评论1",
                "commentTime" : "2018-04-22 22:50:48.39"
            }, 
            {
                "userId" : "tony2",
                "content" : "tony评论2",
                "commentTime" : "2018-04-22 22:51:48.39"
            }, 
            {
                "userId" : "tony3",
                "content" : "tony评论3",
                "commentTime" : "2018-04-22 22:52:48.39"
            }
    ]
};
db.comments.drop(); 
db.comments.insert(comment1);    
db.comments.insert(comment2);  

二、查询练习(pretty只是为了输出好看点)

1、查询所有记录

db.users.find().pretty();
相当于：select * from users;

2、查询去掉后的当前聚集集合中的某列的重复数据

db.users.distinct(“name”);
相当于：select distinct name from users;

3、查询age = 25的记录

db.users.find({“age”:25}).pretty();
相当于：select * from users where age = 25;

4、查询age > 25的记录(大于等于使用$gte)

db.users.find({“age”:{$gt:25}}).pretty();
相当于：select * from users where age > 25;

5、查询age < 25的记录(小于等于使用$lte)

db.users.find({“age”:{$lt:20}}).pretty();
相当于：select * from users where age < 25;

6、查询age >= 25 并且 age <= 26

db.users.find({“age”:{ gte:25, g t e : 25 , lte:26}}).pretty();
相当于：select * from users where age >= 25 and age <= 26;

7、查询name中包含”bu”的数据

db.users.find({“name”:/bu/}).pretty();
相当于：select * from users where name like “%bu%”;

8、查询name中以”ju”开头的

db.users.find({“name”:/^ju/}).pretty();
相当于：select * from users where name like “ju%”;

9、查询指定列name、age数据(只显示name、age的数据)

db.users.find({},{“name”:1,”age”:1}).pretty();
相当于：select name,age from users;

10、查询除了comments以外的数据(只不显示comments的数据)

db.users.find({},{“comments”:0}).pretty();
相当于：select 其它字段 from users;

11、查询指定列name、age数据, age > 25

db.users.find({“age”:{$gt:25}},{“age”:1,”name”:1}).pretty();
相当于：select age,name from users where age > 25;

12、按照年龄排序

升序：db.users.find().sort({“age”:1}).pretty();
相当于：select * from users order by age;
降序：db.users.find().sort({“age”:-1}).pretty();
相当于：select * from users order by age desc;

13、查询前三条数据

db.users.find().limit(3).pretty();
相当于：select * from users limit 3;

14、查询3条以后的数据

db.users.find().skip(3).pretty();
相当于：select * from users where id not in (select id from users limit 3);

15、查询在4-6之间的数据

db.users.find().skip(3).limit(3).pretty();
相当于：select * from users limit 3,3;

16、查询age=25或者age=26的数据

db.users.find({$or:[{“age”:25},{“age”:26}]}).pretty();
相当于：select * from users where age = 25 or age = 26;

17、查询age=25和age=26的数量

db.users.find({$or:[{“age”:25},{“age”:26}]}).count();
相当于：select count(*) from users where age = 25 or age = 26;

18、查询存在评论的数据

db.users.find({“comments”:{$exists:true}}).pretty();
相当于：select * from users where comments is not null;

19、查询favorites.movies中，有”头号玩家”和”肖生克的救赎”的数据

db.users.find({“favorites.movies”:{$all:[“肖生克的救赎”,”头号玩家”]}}).pretty();
相当于：无;

20、查询favorites.movies中，有”头号玩家”,”肖生克的救赎”,”阿甘正传”的数据,且要按该顺序排列的

db.users.find({“favorites.movies”:[“头号玩家”,”肖生克的救赎”,”阿甘正传”]}).pretty();
相当于：无;

21、查询name存在”bu”字符，并且age=25或者26

db.users.find({$and:[{name:{$regex:”.bu.“}},{$or:[{age:25},{age:26}]}]}).pretty();
相当于：无;

22、查询所有的age(数据不重复)

db.users.distinct(“age”);
相当于：select distinct age from users;

22、查询所有name=”xiaobu”的comments前三条数据

db.users.find({“name”:”xiaobu”},{“comments”:{$slice:[0,3]}}).pretty();
相当于：无;

23、查询所有name=”xiaobu”，且comments只显示4-6的评论，且只显示comments和id字段，其它信息不显示

方法一:db.users.find({“name”:”xiaobu”},{“comments”:{$slice:[3,3]},”$elemMatch”:”“}).pretty();
方法二:db.users.find({“name”:”xiaobu”},{“comments”:{“$slice”:[3,3]},”$id”:1}).pretty();(推荐)
相当于：无;

24、精确查询（必须comments的所有字段都匹配才能查询数据来，实际情况基本用不到）

db.users.find({“comments”:{“userId”:”101”,”content”:”评论101”,”commentTime” : “2018-04-22 22:50:48.39”}}).pretty();
相当于：无;

25、查询被userId=101或者userId=001评论过的数据

db.users.find({“comments.userId”:{$in:[“001”,”101”]}}).pretty();
相当于：无;

26、查询userId=101,评语为”评论1”的user

db.users.find({“comments”:{$elemMatch:{“userId”:”101”,”content”:”评论101”}}}).pretty();
相当于：无;

27、查询”_id”等于ObjectId(“5ae20b5e7aec117179c6846c”)的用户评论（dbref查询）

var tom = db.users.findOne({“_id”:ObjectId(“5ae20b5e7aec117179c6846c”)});
var dbref = tom.comments;
db[dbref.$ref].findOne({“_id”:dbref.$id});
相当于子查询