MongoDB 入门系列（八）

为了避免篇幅过长产生阅读疲劳，数组的查询放在第八节

数组查询

1. 新建mongodb-16.js，并输入以下代码

var workmate1={
  name:'JSPang',
  age:33,
  sex:1,
  job:'前端',
  skill:{
      skillOne:'HTML+CSS',
      skillTwo:'JavaScript',
      skillThree:'PHP'
  },
  regeditTime:new Date(),
  interest:['看电影','看书','吃美食','钓鱼','旅游']
}

var workmate2={
  name:'ShengLei',
  age:31,
  sex:1,
  job:'JAVA后端',
  skill:{
      skillOne:'HTML+CSS',
      skillTwo:'J2EE',
      skillThree:'PPT'
  },
  regeditTime:new Date(),
  interest:['篮球','看电影','做饭']
}

var workmate3={
  name:'MinJie',
  age:18,
  sex:0,
  job:'UI',
  skill:{
      skillOne:'PhotoShop',
      skillTwo:'UI',
      skillThree:'PPT'
  },
  regeditTime:new Date(),
  interest:['做饭','画画','看电影']
}
var workmate4={
  name:'XiaoWang',
  age:25,
  sex:1,
  job:'UI',
  skill:{
      skillOne:'PhotoShop',
      skillTwo:'UI',
      skillThree:'PPT'
  },
  regeditTime:new Date(),
  interest:['写代码','篮球','画画']
}
var workmate5={
  name:'LiangPeng',
  age:28,
  sex:1,
  job:'前端',
  skill:{
      skillOne:'HTML+CSS',
      skillTwo:'JavaScript',
  },
  regeditTime:new Date(),
  interest:['玩游戏','写代码','做饭']
}

var workmate6={
  name:'HouFei',
  age:25,
  sex:0,
  job:'前端',
  skill:{
      skillOne:'HTML+CSS',
      skillTwo:'JavaScript',
  },
  regeditTime:new Date(),
  interest:['化妆','读书','做饭']
}

var workmate7={
  name:'LiuYan',
  age:35,
  sex:0,
  job:'美工',
  skill:{
      skillOne:'PhotoShop',
      skillTwo:'CAD',
  },
  regeditTime:new Date(),
  interest:['画画','聚会','看电影']
}


var workmate8={
  name:'DingLu',
  age:20,
  sex:0,
  job:'美工',
  skill:{
      skillOne:'PhotoShop',
      skillTwo:'CAD',
  },
  regeditTime:new Date(),
  interest:['美食','看电影','做饭']
}

var workmate9={
  name:'JiaPeng',
  age:29,
  sex:1,
  job:'前端',
  skill:{
      skillOne:'HTML+CSS',
      skillTwo:'JavaScript',
      skillThree:'PHP'
  },
  regeditTime:new Date(),
  interest:['写代码','篮球','游泳']
}

var workmate10={
  name:'LiJia',
  age:26,
  sex:0,
  job:'前端',
  skill:{
      skillOne:'HTML+CSS',
      skillTwo:'JavaScript',
      skillThree:'PHP'
  },
  regeditTime:new Date(),
  interest:['玩游戏','美食','篮球']
}



var db=connect('company');
var workmateArray=[workmate1,workmate2,workmate3,workmate4,workmate5,workmate6,workmate7,workmate8,workmate9,workmate10];
db.workmate.insert(workmateArray);
print('[SUCCESS]：The data was inserted successfully');

2. 构建并启动mongo

PS D:\Code\Test\Others\MongoDB> mongo .\mongodb-16.js
MongoDB shell version v3.4.4
connecting to: mongodb://127.0.0.1:27017
MongoDB server version: 3.4.4
connecting to: mongodb://127.0.0.1:27017/company
MongoDB server version: 3.4.4
[SUCCESS]：The data was inserted successfully

然后启动mongo

基本查询

> db.workmate.find({interest:['画画','聚会','看电影']},     {name:1,interest:1,age:1,_id:0}  )
{ "name" : "LiuYan", "age" : 35, "interest" : [ "画画", "聚会", "看电影" ] }

可以看到符合条件的只有一条
如果只查询一个条件

> db.workmate.find({interest:['看电影']},
...     {name:1,interest:1,age:1,_id:0}
... )
>

可以看到查询到的为空，问题就在于我们写了一个中括号([]),因为加上中括号就相当于完全匹配了，所以没有得到一条符合查询条件的数据。我们去掉中括号再看看结果。

> db.workmate.find({interest:'看电影'},
...     {name:1,interest:1,age:1,_id:0}
... )
{ "name" : "JSPang", "age" : 33, "interest" : [ "看电影", "看书", "吃美食", "钓鱼", "旅游" ] }
{ "name" : "ShengLei", "age" : 31, "interest" : [ "篮球", "看电影", "做饭" ] }
{ "name" : "MinJie", "age" : 18, "interest" : [ "做饭", "画画", "看电影" ] }
{ "name" : "LiuYan", "age" : 35, "interest" : [ "画画", "聚会", "看电影" ] }
{ "name" : "DingLu", "age" : 20, "interest" : [ "美食", "看电影", "做饭" ] }

所以，如果只是想查询一个条件，就用字符串条件，而不是数组条件
$all-数组多项查询
用$all修饰符，是需要满足所有条件的

db.workmate.find(
    {interest:{$all:["看电影","看书"]}},
    {name:1,interest:1,age:1,_id:0} 
)

$in-数组的或者查询
$in主要满足数组中的一项就可以被查出来（有时候会跟or弄混）

db.workmate.find(
    {interest:{$in:["看电影","看书"]}},
    {name:1,interest:1,age:1,_id:0} 
)

$size-数组个数查询
$size修饰符可以根据数组的数量查询出结果

db.workmate.find(
    {interest:{$size:5}},
    {name:1,interest:1,age:1,_id:0} 
)

$slice-显示选项
有时候我并不需要显示出数组中的所有值，而是只显示前两项，就可以下面这样做

db.workmate.find(
    {},
    {name:1,interest:{$slice:2},age:1,_id:0} 
)

如果我们想显示兴趣的最后一项，可以直接使用slice:-1，来进行查询。

db.workmate.find(
    {},
    {name:1,interest:{$slice:-1},age:1,_id:0} 
)

find参数

• query：这个就是查询条件，MongoDB默认的第一个参数。
• fields：（返回内容）查询出来后显示的结果样式，可以用true和false控制是否显示。
• limit：返回的数量，后边跟数字，控制每次查询返回的结果数量。
• skip:跳过多少个显示，和limit结合可以实现分页。
• sort：排序方式，从小到大排序使用1，从大到小排序使用-1。
  明白了上面这些选项，现在可以作一个最简单的分页，我们把同事集合（collections）进行分页，每页显示两个，并且按照年龄从小到大的顺序排列。

> use company
switched to db company
> db.workmate.find({},{name:true,age:true,_id:false}).limit(0).skip(2).sort({age:1});
{ "name" : "DingLu", "age" : 20 }
{ "name" : "DingLu", "age" : 20 }
{ "name" : "XiaoWang", "age" : 25 }
{ "name" : "HouFei", "age" : 25 }
{ "name" : "XiaoWang", "age" : 25 }
{ "name" : "HouFei", "age" : 25 }
{ "name" : "LiJia", "age" : 26 }
{ "name" : "LiJia", "age" : 26 }
{ "name" : "LiangPeng", "age" : 28 }
{ "name" : "LiangPeng", "age" : 28 }
{ "name" : "JiaPeng", "age" : 29 }
{ "name" : "JiaPeng", "age" : 29 }
{ "name" : "ShengLei", "age" : 31 }
{ "name" : "ShengLei", "age" : 31 }
{ "name" : "JSPang", "age" : 33 }
{ "name" : "JSPang", "age" : 33 }
{ "name" : "LiuYan", "age" : 35 }
{ "name" : "LiuYan", "age" : 35 }

数组查询日常所以比较频繁，需要多加练习，加深记忆