1.指定返回的键

db.[documentName].find ({条件},{键指定})

数据准备persons.json

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 db.persons.insert(persons[i])
}

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

2.查询条件

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”}},false,true)

2.5查询出sex 等于 null的学生

db.persons.find({sex:{$in:[null]}},{country:1})

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})

2.9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)

2.8查询出喜欢的书籍数量是4本的学生

db.persons.find({books:{$size:4}},{_id:0,books:1})

2.9查询出喜欢的书籍数量大于3本的学生

1.增加字段size

db.persons.update({},{$set:{size:4}},false,true)

2.改变书籍的更新方式,每次增加书籍的时候size增加1

db.persons.update({查询器},{$push:{books:”ORACLE”},$inc:{size:1}})

3.利用$gt查询

db.persons.find({size:{$gt:3}})

2.10利用shell查询出Jim喜欢看的书的数量

var persons = db.persons.find({name:"jim"})

while(persons.hasNext()){

obj = persons.next();

print(obj.books.length)

}

课间小结

1.mongodb 是NOSQL数据库但是他在文档查询上还是很强大的

2.查询符基本是用到花括号里面的更新符基本是在外面