MongoDB语法实践

Posted 2020-10-12

####简单操作过程

基本查询：

构造查询数据:

db.test.insert({name:"stephen",age:35,genda:"male",email:"[email protected]"})

db.test.insert({name:"Stephen",age:35,genda:"male",email:"[email protected]"})

db.test.insert({name:"stephen1",age:35,genda:"male",email:"[email protected]"})

db.test.insert({name:"stephen",age:36,genda:"male",email:"[email protected]"})

db.test.insert({name:"stephen",age:37,genda:"male",email:"[email protected]"})

--多条件查询，等同于SQL语句的where name = "stephen" and age = 35

db.test.find({name:"stephen",age:35})

{ "_id" : ObjectId("59f1ae4388f3edba94091894"), "name" : "stephen", "age" : 35, "genda" : "male", "email" : "[email protected]" }

   --返回指定的文档键值对，只返回name和age键值对

    db.test.find({},{name:1,age:1})

    { "_id" : ObjectId("59f1ae4388f3edba94091894"), "name" : "stephen", "age" : 35 }

    { "_id" : ObjectId("59f1ae8588f3edba94091895"), "name" : "stephen", "age" : 36 }

    { "_id" : ObjectId("59f1ae8a88f3edba94091896"), "name" : "stephen", "age" : 37 }

2、查询条件

    MongoDB提供了一组比较操作符：$lt/$lte/$gt/$gte/$ne，依次等价于</<=/>/>=/!=

--返回符合条件age >= 18 && age <= 40的文档

db.test.find({age:{$gte:35,$lte:36}})

    { "_id" : ObjectId("59f1ae4388f3edba94091894"), "name" : "stephen", "age" : 35, "genda" : "male", "email" : "[email protected]" }

    { "_id" : ObjectId("59f1ae8588f3edba94091895"), "name" : "stephen", "age" : 36, "genda" : "male", "email" : "[email protected]" }

--返回指定的键值对条件age >= 18 && age <= 40的文档

db.test.find({age:{$gte:35,$lte:36}},{name:1,age:1})

{ "_id" : ObjectId("59f1ae4388f3edba94091894"), "name" : "stephen", "age" : 35 }

    { "_id" : ObjectId("59f1ae8588f3edba94091895"), "name" : "stephen", "age" : 36 }

--返回条件符合name != "stephen1"

db.test.find({name:{$ne:"stephen"}})

    { "_id" : ObjectId("59f1b20588f3edba94091898"), "name" : "stephen1", "age" : 35, "genda" : "male", "email" : "[email protected]" }

    --$in等同于SQL中的in，下面的示例等同于SQL中的in ("stephen","stephen1")

db.test.find({name:{$in:["stephen","stephen2"]}})

--下面的示例等同于name = "stephen1" or age = 35

db.test.find({$or:[{name:"stephen1"},{age:36}]})

{ "_id" : ObjectId("59f1ae8588f3edba94091895"), "name" : "stephen", "age" : 36, "genda" : "male", "email" : "[email protected]" }

    { "_id" : ObjectId("59f1b20588f3edba94091898"), "name" : "stephen1", "age" : 35, "genda" : "male", "email" : "[email protected]" }

--下面的示例演示了如何混合使用$or和$in

db.test.find({$or:[{name:{$in:["stephen1","setphen12"]}},{age:36}]})

3、NULL数据类型的查询

    --在进行值为null数据的查询时，所有值为null,以及不包括指定键的文档均会被检索出来

    db.test.find({"x":null})

db.test.find({a:null})

    { "_id" : ObjectId("59f1ae4388f3edba94091894"), "name" : "stephen", "age" : 35, "genda" : "male", "email" : "[email protected]" }

    { "_id" : ObjectId("59f1ae8588f3edba94091895"), "name" : "stephen", "age" : 36, "genda" : "male", "email" : "[email protected]" }

    { "_id" : ObjectId("59f1ae8a88f3edba94091896"), "name" : "stephen", "age" : 37, "genda" : "male", "email" : "[email protected]" }

    { "_id" : ObjectId("59f1b1fd88f3edba94091897"), "name" : "stephen", "age" : 35, "genda" : "male", "email" : "[email protected]" }

    { "_id" : ObjectId("59f1b20588f3edba94091898"), "name" : "stephen1", "age" : 35, "genda" : "male", "email" : "[email protected]" }

--再有就是通过$exists判断指定键是否存在

db.test.find({x:{$in:[null],$exists:true}})

    { "_id" : ObjectId("59f1c40b88f3edba94091899"), "x" : null }

4、正则查询

    db.test.find()

--正则语法

db.test.find({name:/1/})

    { "_id" : ObjectId("59f1b20588f3edba94091898"), "name" : "stephen1", "age" : 35, "genda" : "male", "email" : "[email protected]" }

--i表示忽略大小写

db.test.find({name:/stephen?/i})

5、数组数据查询

    db.wqq.insert({name:["aa","bb","cc"]})

db.wqq.insert({name:["aa","ee","cc"]})

    db.wqq.insert({name:["ff","ee","cc"]})

--数组中所有包含banana的文档都会被检索出来

db.wqq.find({name:"aa"})

{ "_id" : ObjectId("59f1c60388f3edba9409189c"), "name" : [ "aa", "bb", "cc" ] }

    { "_id" : ObjectId("59f1c6b988f3edba9409189d"), "name" : [ "aa", "ee", "cc" ] }

--检索数组中需要包含多个元素的情况，这里使用$all。下面的示例中，数组中必须同时包含ff和ee

db.wqq.find({name:{$all:["ff","cc"]}})

{ "_id" : ObjectId("59f1c6ba88f3edba9409189e"), "name" : [ "ff", "ee", "cc" ] }

--精确匹配即被检索出来的文档，name值中的数组数据必须和查询条件完全匹配，即不能多，也不能少，顺序也必须保持一致

    db.wqq.find({name:["ff","ee","cc"]})

{ "_id" : ObjectId("59f1c6ba88f3edba9409189e"), "name" : [ "ff", "ee", "cc" ] }

--匹配数组中指定下标元素的值，数组的起始下标是0

db.wqq.find({"name.1":"bb"})

    { "_id" : ObjectId("59f1c60388f3edba9409189c"), "name" : [ "aa", "bb", "cc" ] }

--可以通过$size获取数组的长度，但是$size不能和比较操作符联合使用

db.wqq.find({"name":{$size:3}})

    { "_id" : ObjectId("59f1c60388f3edba9409189c"), "name" : [ "aa", "bb", "cc" ] }

    { "_id" : ObjectId("59f1c6b988f3edba9409189d"), "name" : [ "aa", "ee", "cc" ] }

    { "_id" : ObjectId("59f1c6ba88f3edba9409189e"), "name" : [ "ff", "ee", "cc" ] }

--如果需要检索size > n的结果，不能直接使用$size，只能是添加一个额外的键表示数据中的元素数据，在操作数据中的元素时，需要同时更新size键的值

--为后面的实验构造数据

db.wqq.update({}, {"$set": {"size":3}},false,true)

    WriteResult({ "nMatched" : 3, "nUpserted" : 0, "nModified" : 3 })

    > db.wqq.find()

    { "_id" : ObjectId("59f1c60388f3edba9409189c"), "name" : [ "aa", "bb", "cc" ], "size" : 3 }

    { "_id" : ObjectId("59f1c6b988f3edba9409189d"), "name" : [ "aa", "ee", "cc" ], "size" : 3 }

    { "_id" : ObjectId("59f1c6ba88f3edba9409189e"), "name" : [ "ff", "ee", "cc" ], "size" : 3 }

--每次添加一个新元素，都要原子性的自增size一次

db.wqq.update({},{$push:{name:123},$inc:{size:1}},0,1)

    WriteResult({ "nMatched" : 3, "nUpserted" : 0, "nModified" : 3 })

    > db.wqq.find()

    { "_id" : ObjectId("59f1c60388f3edba9409189c"), "name" : [ "aa", "bb", "cc", 123 ], "size" : 4 }

    { "_id" : ObjectId("59f1c6b988f3edba9409189d"), "name" : [ "aa", "ee", "cc", 123 ], "size" : 4 }

    { "_id" : ObjectId("59f1c6ba88f3edba9409189e"), "name" : [ "ff", "ee", "cc", 123 ], "size" : 4 }

--通过$slice返回数组中的部分数据。"$slice":2表示数组中的前两个元素

db.wqq.find({},{name:{$slice:2},size:0})   //若为负数则是最后2个元素

    { "_id" : ObjectId("59f1c60388f3edba9409189c"), "name" : [ "aa", "bb" ] }

    { "_id" : ObjectId("59f1c6b988f3edba9409189d"), "name" : [ "aa", "ee" ] }

    { "_id" : ObjectId("59f1c6ba88f3edba9409189e"), "name" : [ "ff", "ee" ] }

--$slice : [2,1]，表示从第二个2元素开始取1个，如果获取数量大于2后面的元素数量，则取后面的全部数据

db.wqq.find({},{name:{$slice:[2,1]}})

db.wqq.find({},{name:{$slice:[2,1]},size:0})

   { "_id" : ObjectId("59f1c60388f3edba9409189c"), "name" : [ "cc" ] }

   { "_id" : ObjectId("59f1c6b988f3edba9409189d"), "name" : [ "cc" ] }

   { "_id" : ObjectId("59f1c6ba88f3edba9409189e"), "name" : [ "cc" ] }

6、内嵌文档查询

    --当嵌入式文档为数组时，需要$elemMatch操作符来帮助定位某一个元素匹配的情况，否则嵌入式文件将进行全部的匹配

    --即检索时需要将所有元素都列出来作为查询条件方可

    db.aa.insert({comments:[{author:"sharesoe",score:3},{author:"mary",score:6}]})

    WriteResult({ "nInserted" : 1 })

    > db.aa.find()

    { "_id" : ObjectId("59f1cc8e88f3edba9409189f"), "comments" : [ { "author" : "sharesoe", "score" : 3 }, { "author" : "mary", "score" : 6 } ] }

  --

db.aa.find({comments:{$elemMatch:{author:"sharesoe",score:{$gte:3}}}})

    { "_id" : ObjectId("59f1cc8e88f3edba9409189f"), "comments" : [ { "author" : "sharesoe", "score" : 3 }, { "author" : "mary", "score" : 6 } ] }

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