集腋成裘-15-MongoDB系列-02Find详细

var persons = [{
    name:"jim",
    age:25,
    email:"75431457@qq.com",
    c:89,m:96,e:87,
    country:"USA",
    books:["JS","C++","EXTJS","MONGODB"]
},
{
    name:"tom",
    age:25,
    email:"214557457@qq.com",
    c:75,m:66,e:97,
    country:"USA",
    books:["PHP","JAVA","EXTJS","C++"]
},
{
    name:"lili",
    age:26,
    email:"344521457@qq.com",
    c:75,m:63,e:97,
    country:"USA",
    books:["JS","JAVA","C#","MONGODB"]
},
{
    name:"zhangsan",
    age:27,
    email:"2145567457@qq.com",
    c:89,m:86,e:67,
    country:"China",
    books:["JS","JAVA","EXTJS","MONGODB"]
},
{
    name:"lisi",
    age:26,
    email:"274521457@qq.com",
    c:53,m:96,e:83,
    country:"China",
    books:["JS","C#","PHP","MONGODB"]
},
{
    name:"wangwu",
    age:27,
    email:"65621457@qq.com",
    c:45,m:65,e:99,
    country:"China",
    books:["JS","JAVA","C++","MONGODB"]
},
{
    name:"zhaoliu",
    age:27,
    email:"214521457@qq.com",
    c:99,m:96,e:97,
    country:"China",
    books:["JS","JAVA","EXTJS","PHP"]
},
{
    name:"piaoyingjun",
    age:26,
    email:"piaoyingjun@uspcat.com",
    c:39,m:54,e:53,
    country:"Korea",
    books:["JS","C#","EXTJS","MONGODB"]
},
{
    name:"lizhenxian",
    age:27,
    email:"lizhenxian@uspcat.com",
    c:35,m:56,e:47,
    country:"Korea",
    books:["JS","JAVA","EXTJS","MONGODB"]
},
{
    name:"lixiaoli",
    age:21,
    email:"lixiaoli@uspcat.com",
    c:36,m:86,e:32,
    country:"Korea",
    books:["JS","JAVA","PHP","MONGODB"]
},
{
    name:"zhangsuying",
    age:22,
    email:"zhangsuying@uspcat.com",
    c:45,m:63,e:77,
    country:"Korea",
    books:["JS","JAVA","C#","MONGODB"]
}]
for(var i = 0;i<persons.length;i++){
    db.persons.insert(persons[i])
}
var persons = db.persons.find({name:"jim"})
while(persons.hasNext()){
    obj = persons.next();
        print(obj.books.length)
} 

find：db.集合名.find({条件},{键指定})
1：只查找部分字段
       1.1 查询出所有数据的指定键(name ,age ,country)
       db.persons.find({},{name:1,age:1,country:1,_id:0});
2.查询条件
       $gte $gt $lte $lt  $ne
        2.1查询出年龄在25到27岁之间的学生
       db.persons.find({age: {$gte:25,$lte:27},{_id:0,age:1})
       2.2查询出所有不是韩国籍的学生的数学成绩
       db.persons.find({country:{$ne:” Korea”}},{_id:0,m:1})
3.包含或不包含
       $in或$nin
       2.3查询国籍是中国或美国的学生信息
       db.persons.find({country:{$in:[“USA”,“China”]}})
       2.4查询国籍不是中国或美国的学生信息
       db.persons.find({country:{$nin:[“USA”,“China”]}})
4.OR查询
      $or
      2.4查询语文成绩大于85或者英语大于90的学生信息
      db.persons.find({$or:[{c:{$gte:85}},{e:{$gte:90}}]},{_id:0,c:1,e:1})
5.Null
      把中国国籍的学生上增加新的键sex
      db.person.update({country:”China”},{$set:{sex:”m”}})
      2.5查询出sex 等于 null的学生
      db.persons.find({sex:{$in:[null]}},{country:1})
      或者db.persons.find({sex:{$eq:null}})
6.正则查询
        2.6查询出名字中存在”li”的学生的信息
        db.persons.find({name:/li/i},{_id:0,name:1}) 
7.$not的使用
      $not可以用到任何地方进行取反操作
        2.7查询出名字中不存在”li”的学生的信息
        db.persons.find({name:{$not:/li/i}},{_id:0,name:1})
        $not和$nin的区别是$not可以用在任何地方儿$nin是用到集合上的
8.数组查询$all和index应用
        2.8查询喜欢看MONGOD和JS的学生
       db.persons.find({books:{$all:[“MONGOBD”,”JS”]}},{books:1,_id:0})
       2.8.2查询第二本书是JAVA的学习信息
       db.persons.find({“books.1”:”JAVA”})
9.查询指定长度数组$size它不能与比较查询符一起使用(这是弊端)
       2.9查询出喜欢的书籍数量小于4本的学生
        db.persons.find({$where:"this.books.length《4"})
       2.9.2查询出lili喜欢看的书的数量     
        var lili = db.persons.find({name:"lili"})
        while(lili.hasNext()){
            obj=lili.next()
            print(obj.books.length)
        }  
10.$slice操作符返回文档中指定数组的内部值
       2.10查询出Jim书架中第2~4本书
       db.persons.find({name:"jim"},{books:{"$slice":[1,3]}})
       2.10.2查询出最后一本书
      db.persons.find({name:"jim"},{books:{"$slice":-1},_id:0,name:1})    

var jim = [{
    school :"K",
    score:"A"
},{
    school :"L",
    score:"B"
},{
    school :"J",
    score:"A+"
}]
db.persons.update({name:"jim"},{$set:{school:jim}})

3.文档查询
    3.1查询出在K上过学的学生
        db.persons.find({"school.school":"K"})
    3.2查询出在K上过学的学生，而且成绩中获得过A的学生
        db.persons.find({"school.school":"K","school.score":"A"})
    3.3查询出在K校成绩为A的学生
        db.persons.find({school:{$elemMatch:{"school":"K","score":"A"}}})
4.$where
    4.查询年龄大于22岁,喜欢看C#书,在K学校上过学的学生信息
        db.persons.find({age:22,books:{$in:["C#"]},"school.school":"K"})
        或者
        db.persons.find({"$where":function(){
            //得到查询结果的每一条文档
            var books = this.books;
            //得到文档中的school对象
            var school = this.school;
            //如果年纪>=22
            if(this.age > 22){
                var php = null;
                //遍历书籍
                for ( var i = 0; i < books.length; i++) {
                    if(books[i] == "C++"){
                        php = books[i];
                        //如果学校是真
                        if(school){
                            for (var j = 0; j < school.length; j++) {
                                //判断是不是在K上学
                                if(school[j].school == "K"){
                                    //返回是真
                                    return true;
                                }
                            }
                            break;
                        }
                    }
                }    
            }
        }})
5.Limit返回指定的数据条数
    5.1查询出persons文档中前5条数据
    db.persons.find({},{_id:0,name:1}).limit(5)
6.Skip返回指定数据的跨度
    6.1查询出persons文档中5~10条的数据
    db.persons.find({},{_id:0,name:1}).limit(5).skip(5)
7.Sort返回按照年龄排序的数据[1,-1]
    db.persons.find({},{_id:0,name:1,age:1}).sort({age:1})
    注意:mongodb的key可以存不同类型的数据排序就也有优先级
    最小值
    null
    数字
    字符串
    对象/文档
    数组
    二进制
    对象ID
    布尔
    日期
     时间戳  正则  最大值  
8：分页（跳过多少条，去多少条）
    db.persons.find().limit(5).skip(5).sort({id:1})
    注意：分页的性能不好，建议通过，筛选条件+limit()，获取分页
    示例：根据自增的id取数据（每页5条，显示第二页）
     方法一：db.persons.find().limit(5).skip(5)
     方法二：db.persons.find({id:{$gt:5}}).limit(5) 
    而且，应该把重点放到便捷和精确查询上而不是分页的性能上
因为用户最多不会翻查过2页的