文章目录

  • Mongodb使用学习笔记(二)之查询篇
    • 1. MongoDB命令学习
      • (1) MongoDB 查询文档
        • 1.1 全部查询
        • 1.2 单条件查询
        • 1.3 多条件查询
          • 1.3.1 AND拼接多条件查询
          • 1.3.1 OR拼接多条件查询
          • 1.3.1 AND和or混用拼接多条件查询
        • 1.4 模糊查询
        • 1.5 排序查询
        • 1.6 聚合查询

Mongodb使用学习笔记(二)之查询篇

  • 参考：菜鸟教程

1. MongoDB命令学习

(1) MongoDB 查询文档

1.1 全部查询
  • db.collection.find() 方法，查询全部文档，查询结果不会进行json格式化。

    • 不改变参数和全部文档内容情况下，每次查询回来的结果顺序是一样的。
  • db.collection.find().pretty()方法，查询全部文档，查询结果会进行json格式化。
  • db.collection.findOne(), 返回db.collection.find() 查询数组的第一个文档。
1.2 单条件查询
  • 单条件精确比较匹配：filterKey是文档中的属性，filterValue是要过滤的条件值（精确匹配）。

    db.collection.find({"filterKey":"filterValue"})
  • 单条件范围比较匹配：filterKey是文档中的属性，filterValue是要比较的条件值）。
  • 注意事项：filterValue的类型，如果是数字，那就不用加引号，比较的是数字大小。如果是加了引号，就是字符串，比较的是字典序。
  • 比较符号：
    • 小于： lt
    • 小于等于： lte
    • 大于：gt
    • 大于等于：gte
    • 不等于：ne
    db.collection.find(   {<filterKey>:{$lt:<filterValue>}})
  • 操作记录： 
    > show dbs;
admin   0.000GB
cmdb    0.000GB
config  0.000GB
local   0.000GB
> use cmdb
switched to db cmdb
> show db.collections;
uncaught exception: Error: don't know how to show [db.collections] :
shellHelper.show@src/mongo/shell/utils.js:1211:11
shellHelper@src/mongo/shell/utils.js:838:15
@(shellhelp2):1:1
> show collections;
hardware
> db.ha
db.hardware        db.hasOwnProperty
> db.hardware.insert({"name":"一个大丑逼","age":"20","hobbies":["eat"]})
WriteResult({ "nInserted" : 1 })
> db.hardware.find();
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
> db.hardware.insert({"name":"一个大帅逼","age":"18","hobbies":["piano","cooking","reading","game"]});
WriteResult({ "nInserted" : 1 })
> db.hardware.find();
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
> db.hardware.find().pretty();
{"_id" : ObjectId("619f2b73cec1a85ec6147ad3"),"name" : "一个大丑逼","age" : "20","hobbies" : ["eat"]
}
{"_id" : ObjectId("619f2c3ccec1a85ec6147ad4"),"name" : "一个大帅逼","age" : "18","hobbies" : ["piano","cooking","reading","game"]
}
> db.hardware.find("name", "一个大丑逼");
Error: error: {"ok" : 0,"errmsg" : "Executor error during find command :: caused by :: ReferenceError: name is not defined :\n@:1:15\n","code" : 139,"codeName" : "JSInterpreterFailure"
}
> db.hardware.find("name":"一个大丑逼");
uncaught exception: SyntaxError: missing ) after argument list :
@(shell):1:23
> db.hardware.find({"name":"一个大丑逼"});
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
> db.hardware.find({"age":{$lt:20}});
> db.hardware.find({"age":{$1t:20}});
Error: error: {"ok" : 0,"errmsg" : "unknown operator: $1t","code" : 2,"codeName" : "BadValue"
}
> db.hardware.find({"age":{$lt:25}});
> db.hardware.find();
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
> db.hardware.find({"age":{$lt:25}});
> db.hardware.find({"age":{$lt:"25"}});
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
> db.hardware.find({"age":{$lt:"WSSB"}});
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
> db.hardware.find({"age":{$lt:"19"}});
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
> db.hardware.find({"age":{$lt:"190"}});
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
>
1.3 多条件查询
1.3.1 AND拼接多条件查询
  • 多个条件用逗号隔开就行了，样式如：db.collection.find({key1:value1, key2:value2})
  • 操作记录 
    > use cmdb;
switched to db cmdb
> db.hardware.insert({"name":"hardware1","serial_number":"0000001","type":"route                                                                            r","city":"gz"})
WriteResult({ "nInserted" : 1 })
> db.hardware.insert({"name":"hardware2","serial_number":"0000002","type":"route                                                                            r","city":"gz"})
WriteResult({ "nInserted" : 1 })
> db.hardware.insert({"name":"hardware3","serial_number":"0000003","type":"route                                                                            r","city":"gz"})
WriteResult({ "nInserted" : 1 })
> db.hardware.insert({"name":"hardware4","serial_number":"0000004","type":"switc                                                                            h","city":"gz"})
WriteResult({ "nInserted" : 1 })
> db.hardware.insert({"name":"hardware5","serial_number":"0000005","type":"switc                                                                            h","city":"hn"})
WriteResult({ "nInserted" : 1 })
> db.hardware.find();
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
{ "_id" : ObjectId("61a4a21adf090cc7b1fddfbc"), "name" : "hardware1", "serial_number" : "0000001", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a243df090cc7b1fddfbd"), "name" : "hardware2", "serial_number" : "0000002", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a24ddf090cc7b1fddfbe"), "name" : "hardware3", "serial_number" : "0000003", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a267df090cc7b1fddfbf"), "name" : "hardware4", "serial_number" : "0000004", "type" : "switch", "city" : "gz" }
{ "_id" : ObjectId("61a4a27bdf090cc7b1fddfc0"), "name" : "hardware5", "serial_number" : "0000005", "type" : "switch", "city" : "hn" }
> db.hardware.find({"name":"hardware1","city":"gz"}).pretty();
{"_id" : ObjectId("61a4a21adf090cc7b1fddfbc"),"name" : "hardware1","serial_number" : "0000001","type" : "router","city" : "gz"
}
> db.hardware.find({"city":"gz"}).pretty();
{"_id" : ObjectId("61a4a21adf090cc7b1fddfbc"),"name" : "hardware1","serial_number" : "0000001","type" : "router","city" : "gz"
}
{"_id" : ObjectId("61a4a243df090cc7b1fddfbd"),"name" : "hardware2","serial_number" : "0000002","type" : "router","city" : "gz"
}
{"_id" : ObjectId("61a4a24ddf090cc7b1fddfbe"),"name" : "hardware3","serial_number" : "0000003","type" : "router","city" : "gz"
}
{"_id" : ObjectId("61a4a267df090cc7b1fddfbf"),"name" : "hardware4","serial_number" : "0000004","type" : "switch","city" : "gz"
}
>
1.3.1 OR拼接多条件查询
  • 使用了关键字 $or。中括号里面是并列条件的列表
  • 语法格式： 
    >db.collection.find({$or: [{key1: value1}, {key2:value2}]}
)
1.3.1 AND和or混用拼接多条件查询
  • 例一：查询 “city"为"gz"或者"hn”，并且"name"为"hardware1"或者"hardware2"的数据
  • 伪代码： （data.get(“city”).equals(“gz”) || data.get(“city”).equals(“hn”) ） && (data.get(“name”).equals(“hardware1”) || data.get(“name”).equals(“hardware2”))- 
    > db.hardware.find({$and:[{$or:[{"name":"hardware1"},{"name":"hardware2"}]},{$or:[{"city":"gz"},{"city":"hn"}]}]}).pretty();
{"_id" : ObjectId("61a4a21adf090cc7b1fddfbc"),"name" : "hardware1","serial_number" : "0000001","type" : "router","city" : "gz"
}
{"_id" : ObjectId("61a4a243df090cc7b1fddfbd"),"name" : "hardware2","serial_number" : "0000002","type" : "router","city" : "gz"
}
>
  • 例二：查询 “name"为"hardware1"且"type"为"router” 或者 “city"为"gz"且"type"为"switch”
  • 伪代码：（data.get(“name”).equals(“hardware1”) && data.get(“type”).equals(“router”) ） || (data.get(“city”).equals(“gz”) && data.get(“type”).equals(“switch”)) 
    > db.hardware.find({$or:[{$and:[{"name":"hardware1"},{"type":"router"}]},{$and:[{"city":"gz"},{"type":"                                                                            switch"}]}]}).pretty();
{"_id" : ObjectId("61a4a21adf090cc7b1fddfbc"),"name" : "hardware1","serial_number" : "0000001","type" : "router","city" : "gz"
}
{"_id" : ObjectId("61a4a267df090cc7b1fddfbf"),"name" : "hardware4","serial_number" : "0000004","type" : "switch","city" : "gz"
}
>
  • 注意事项：
    • 1.$and和$or后面跟的都是中括号[]
    • 2.子条件条件要用{}括起来（相当于where中的小括号()）
1.4 模糊查询

  • 模糊查询可以使用正则表达式

  • MongoDB 正则表达式

  • MongoDB 使用 $regex 操作符来设置匹配字符串的正则表达式。

    • {$regex:“value”}表示对value进行模糊匹配。注意，{$regex:“value”}还可以对数组中的元素进行模糊匹配。
    db.collection.find({ key:{$regex:"value"} })

  • MongoDB使用PCRE (Perl Compatible Regular Expression) 作为正则表达式语言。

  • 正则表达式

  • 两条正斜杠：正斜杠之间包含着要匹配的规则，本身实际上没啥意义。

  • 下面的方法表示对value进行迷糊匹配，和db.collection.find({ key:{$regex:“value”} })等价

    db.collection.find({ key: /value/ })

  • value可以替换为相应的正则表达式，表示对符合该正则表达式的值进行匹配。

  • 注意事项：

    • 1.正则表达式是对字符串进行匹配，对数字不行
    • 2.key带不带双引号不影响结果，但是两种形式中的value的双引号要注意 ，会影响匹配的结果。

  • 操作记录：

    • 3./^d/表示字符串以d开头，所以有"def"和"defg"符合。/^g/ 表示g开头，没有符合的。
    • 4.Mongodb正则表达式还可以忽略大小写进行匹配：db.collection.find({ key:{$regex:“value”,$options:"$i"} })
    • 正则表达式中使用变量。一定要使用eval将组合的字符串进行转换，不能直接将字符串拼接后传入给表达式。否则没有报错信息，只是结果为空！
    > db.hardware.find();
{ "_id" : ObjectId("61a8674e83e24c27ab4ce164"), "name" : "hardware6asdg", "serial_number" : "abcdef", "type" : "switch", "city" : "hn" }
{ "_id" : ObjectId("61a8677d83e24c27ab4ce165"), "name" : "hardware7scd", "serial_number" : "ab123bc", "type" : "switch", "city" : "bj" }
{ "_id" : ObjectId("61a867fd83e24c27ab4ce166"), "name" : "hardwareqwer", "serial_number" : "aswd5678", "type" : "hostmachine", "city" : "js" }
{ "_id" : ObjectId("61a8698ddec81e3abc4b7d13"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ 12, 34, 567 ]}
> db.hardware.find({name:{$regex:"hardware"}});
{ "_id" : ObjectId("61a8674e83e24c27ab4ce164"), "name" : "hardware6asdg", "serial_number" : "abcdef", "type" : "switch", "city" : "hn" }
{ "_id" : ObjectId("61a8677d83e24c27ab4ce165"), "name" : "hardware7scd", "serial_number" : "ab123bc", "type" : "switch", "city" : "bj" }
{ "_id" : ObjectId("61a867fd83e24c27ab4ce166"), "name" : "hardwareqwer", "serial_number" : "aswd5678", "type" : "hostmachine", "city" : "js" }
{ "_id" : ObjectId("61a8698ddec81e3abc4b7d13"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ 12, 34, 567]}
> db.hardware.find({name:{$regex:"hardware6"}});
{ "_id" : ObjectId("61a8674e83e24c27ab4ce164"), "name" : "hardware6asdg", "serial_number" : "abcdef", "type" : "switch", "city" : "hn" }
> db.hardware.find({name:/hardware6/});
{ "_id" : ObjectId("61a8674e83e24c27ab4ce164"), "name" : "hardware6asdg", "serial_number" : "abcdef", "type" : "switch", "city" : "hn" }
> db.hardware.find({"name":/hardware6/});
{ "_id" : ObjectId("61a8674e83e24c27ab4ce164"), "name" : "hardware6asdg", "serial_number" : "abcdef", "type" : "switch", "city" : "hn" }
> db.hardware.find({"name":/"hardware6"/});
> db.hardware.find({"name":{$regex:"hardware6"}});
{ "_id" : ObjectId("61a8674e83e24c27ab4ce164"), "name" : "hardware6asdg", "serial_number" : "abcdef", "type" : "switch", "city" : "hn" }
> db.hardware.find({"name":{$regex:hardware6}});
uncaught exception: ReferenceError: hardware6 is not defined :
@(shell):1:27
> db.hardware.find({"port":{$regex:"567"}});
> db.hardware.find({"port":{$regex:567}});
Error: error: {"ok" : 0,"errmsg" : "$regex has to be a string","code" : 2,"codeName" : "BadValue"
}
> db.hardware.insert({"name":"hardwarecvbn","serial_number":"5201314","type":"switch","city":"hn","port":["abc","def"]})
WriteResult({ "nInserted" : 1 })
> db.hardware.insert({"name":"hardwarecvbn","serial_number":"5201314","type":"switch","city":"hn","port":["ab","defg"]})
WriteResult({ "nInserted" : 1 })
> db.hardware.find({"port":{$regex:"abc"}});
{ "_id" : ObjectId("61a86bf0dec81e3abc4b7d14"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ] }
> db.hardware.find({"port":{$regex:"bc"}});
{ "_id" : ObjectId("61a86bf0dec81e3abc4b7d14"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ] }
> db.hardware.find({"port":{$regex:"ab"}});
{ "_id" : ObjectId("61a86bf0dec81e3abc4b7d14"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ] }
{ "_id" : ObjectId("61a86c01dec81e3abc4b7d15"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ "ab", "defg" ] }
> db.hardware.find({"port":{$regex:"g"}});
{ "_id" : ObjectId("61a86c01dec81e3abc4b7d15"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ "ab", "defg" ] }
> db.hardware.find({"port":/^d/});
{ "_id" : ObjectId("61a86bf0dec81e3abc4b7d14"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ] }
{ "_id" : ObjectId("61a86c01dec81e3abc4b7d15"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ "ab", "defg" ] }
> db.hardware.find({"port":/^g/});
>
1.5 排序查询
  • 使用sort()进行排序。两个参数，第一个指明排序的字段，第二个参数为1或者-1。1是升序，-1是降序。
  • 语法：db.collection.find().sort({key:-1})
  • 注意事项：
    • 1.正序时，“不包含排序字段的数据”要排在“包含排序字段的数据”前面
    • 2.“不包含排序字段的数据”在sort()之后也会排序，而且是通过"_id"来排序
    • 3.如果要对多个字段进行排序：格式是：db.collection.find().sort({key1:1,key2:1})
    • 4.多个字段进行排序时，优先排序前面的key，以前面key的排序结果为主。（看下列serial_number和index的排序）
    > db.hardware.find()
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
{ "_id" : ObjectId("61a4a21adf090cc7b1fddfbc"), "name" : "hardware1", "serial_number" : "0000001", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a243df090cc7b1fddfbd"), "name" : "hardware2", "serial_number" : "0000002", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a24ddf090cc7b1fddfbe"), "name" : "hardware3", "serial_number" : "0000003", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a267df090cc7b1fddfbf"), "name" : "hardware4", "serial_number" : "0000004", "type" : "switch", "city" : "gz" }
{ "_id" : ObjectId("61a4a27bdf090cc7b1fddfc0"), "name" : "hardware5", "serial_number" : "0000005", "type" : "switch", "city" : "hn" }
> db.hardware.find().sort({"age":1})
{ "_id" : ObjectId("61a4a21adf090cc7b1fddfbc"), "name" : "hardware1", "serial_number" : "0000001", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a243df090cc7b1fddfbd"), "name" : "hardware2", "serial_number" : "0000002", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a24ddf090cc7b1fddfbe"), "name" : "hardware3", "serial_number" : "0000003", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a267df090cc7b1fddfbf"), "name" : "hardware4", "serial_number" : "0000004", "type" : "switch", "city" : "gz" }
{ "_id" : ObjectId("61a4a27bdf090cc7b1fddfc0"), "name" : "hardware5", "serial_number" : "0000005", "type" : "switch", "city" : "hn" }
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
> db.hardware.insert({"name":"hardwarecvbn","serial_number":"5201314","type":"switch","city":"hn","port":["abc","def"]})
WriteResult({ "nInserted" : 1 })
> db.hardware.insert({"name":"hardwarecvbn","serial_number":"5200000","type":"switch","city":"hn","port":["abc","def"],"index":1})
WriteResult({ "nInserted" : 1 })
> db.hardware.insert({"name":"hardwarecvbn","serial_number":"5200001","type":"switch","city":"hn","port":["abc","def"],"index":0})
WriteResult({ "nInserted" : 1 })
> db.hardware.find().sort({"serial_number":1})
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
{ "_id" : ObjectId("61a4a21adf090cc7b1fddfbc"), "name" : "hardware1", "serial_number" : "0000001", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a243df090cc7b1fddfbd"), "name" : "hardware2", "serial_number" : "0000002", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a24ddf090cc7b1fddfbe"), "name" : "hardware3", "serial_number" : "0000003", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a267df090cc7b1fddfbf"), "name" : "hardware4", "serial_number" : "0000004", "type" : "switch", "city" : "gz" }
{ "_id" : ObjectId("61a4a27bdf090cc7b1fddfc0"), "name" : "hardware5", "serial_number" : "0000005", "type" : "switch", "city" : "hn" }
{ "_id" : ObjectId("61a88a4ce890d78678783ccc"), "name" : "hardwarecvbn", "serial_number" : "5200000", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ], "index" : 1 }
{ "_id" : ObjectId("61a88a5ae890d78678783ccd"), "name" : "hardwarecvbn", "serial_number" : "5200001", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ], "index" : 0 }
{ "_id" : ObjectId("61a88a27e890d78678783ccb"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ] }
> db.hardware.find().sort({"serial_number":1,"index":1})
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
{ "_id" : ObjectId("61a4a21adf090cc7b1fddfbc"), "name" : "hardware1", "serial_number" : "0000001", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a243df090cc7b1fddfbd"), "name" : "hardware2", "serial_number" : "0000002", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a24ddf090cc7b1fddfbe"), "name" : "hardware3", "serial_number" : "0000003", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a267df090cc7b1fddfbf"), "name" : "hardware4", "serial_number" : "0000004", "type" : "switch", "city" : "gz" }
{ "_id" : ObjectId("61a4a27bdf090cc7b1fddfc0"), "name" : "hardware5", "serial_number" : "0000005", "type" : "switch", "city" : "hn" }
{ "_id" : ObjectId("61a88a4ce890d78678783ccc"), "name" : "hardwarecvbn", "serial_number" : "5200000", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ], "index" : 1 }
{ "_id" : ObjectId("61a88a5ae890d78678783ccd"), "name" : "hardwarecvbn", "serial_number" : "5200001", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ], "index" : 0 }
{ "_id" : ObjectId("61a88a27e890d78678783ccb"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ] }
> db.hardware.find().sort({"index":1,"serial_number":1})
{ "_id" : ObjectId("619f2b73cec1a85ec6147ad3"), "name" : "一个大丑逼", "age" : "20", "hobbies" : [ "eat" ] }
{ "_id" : ObjectId("619f2c3ccec1a85ec6147ad4"), "name" : "一个大帅逼", "age" : "18", "hobbies" : [ "piano", "cooking", "reading", "game" ] }
{ "_id" : ObjectId("61a4a21adf090cc7b1fddfbc"), "name" : "hardware1", "serial_number" : "0000001", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a243df090cc7b1fddfbd"), "name" : "hardware2", "serial_number" : "0000002", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a24ddf090cc7b1fddfbe"), "name" : "hardware3", "serial_number" : "0000003", "type" : "router", "city" : "gz" }
{ "_id" : ObjectId("61a4a267df090cc7b1fddfbf"), "name" : "hardware4", "serial_number" : "0000004", "type" : "switch", "city" : "gz" }
{ "_id" : ObjectId("61a4a27bdf090cc7b1fddfc0"), "name" : "hardware5", "serial_number" : "0000005", "type" : "switch", "city" : "hn" }
{ "_id" : ObjectId("61a88a27e890d78678783ccb"), "name" : "hardwarecvbn", "serial_number" : "5201314", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ] }
{ "_id" : ObjectId("61a88a5ae890d78678783ccd"), "name" : "hardwarecvbn", "serial_number" : "5200001", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ], "index" : 0 }
{ "_id" : ObjectId("61a88a4ce890d78678783ccc"), "name" : "hardwarecvbn", "serial_number" : "5200000", "type" : "switch", "city" : "hn", "port" : [ "abc", "def" ], "index" : 1 }
>
1.6 聚合查询
  • MongoDB 聚合
  • 使用aggregate()方法
  • 格式：
    • value1是聚合的分组参数，可以是常量也可以是变量，如果是常量那么会把全部的文档数据分在常量这个组，如果是文档中的字段的话则会按照这个字段分组。
    • name1是自定义的名称，聚合结果的列名。
    • $symbol1是聚合表达式，主要有：$sum, $avg,$min等，具体可以查看MongoDB 聚合
    • field1是要聚合的参数，可以是常量也可以是变量。如果是常量，那么聚合结果就是这个常量。如果是文档中的字段，那么会对这个字段进行聚合。 
      db.collection.aggregate([{ $group:{ "_id":value1,name1:{$symbol1:$field1} } }])
  • 注意事项：
    • 1.聚合函数的参数由中括号[]括起来的
    • 2.每一个聚合的条件是在一个 {$group:{}}结构里面，$group是固定的
    • 3.分组的参数的key一定要是"_id",不然会报错：“The field ‘xxx’ must be an accumulator object”
    • 4.想要对全部文档做聚合，可以对常量分组
  • 操作记录： 
    > db.people.aggregate([{$group:{"id_":"$age",sum_:{$sum:1}}}])
uncaught exception: Error: command failed: {"ok" : 0,"errmsg" : "The field 'id_' must be an accumulator object","code" : 40234,"codeName" : "Location40234"
} with original command request: {"aggregate" : "people","pipeline" : [{"$group" : {"id_" : "$age","sum_" : {"$sum" : 1}}}],"cursor" : {},"lsid" : {"id" : UUID("20ef3a49-89bd-4377-821d-300f9ca9be6b")}
} on connection: connection to 127.0.0.1:27017 : aggregate failed :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
doassert@src/mongo/shell/assert.js:18:14
_assertCommandWorked@src/mongo/shell/assert.js:737:17
assert.commandWorked@src/mongo/shell/assert.js:829:16
DB.prototype._runAggregate@src/mongo/shell/db.js:276:5
DBCollection.prototype.aggregate@src/mongo/shell/collection.js:1058:12
@(shell):1:1
> db.people.aggregate([{$group:{"_id":"$age",sum_:{$sum:1}}}])
{ "_id" : 22, "sum_" : 1 }
{ "_id" : 26, "sum_" : 1 }
{ "_id" : 23, "sum_" : 1 }
> db.people.aggregate([{$group:{"_id":"$age",sum_:{$sum:"$salary"}}}])
{ "_id" : 23, "sum_" : 7000 }
{ "_id" : 26, "sum_" : 10000 }
{ "_id" : 22, "sum_" : 6000 }
> db.people.insert({"id":"004","age":26,"salary":12000})
WriteResult({ "nInserted" : 1 })
> db.people.aggregate([{$group:{"_id":"$age",sum_:{$avg:"$salary"}}}])
{ "_id" : 22, "sum_" : 6000 }
{ "_id" : 26, "sum_" : 11000 }
{ "_id" : 23, "sum_" : 7000 }
> db.people.aggregate([{$group:{"_id":"$age",sum_:{$min:"$salary"}}}])
{ "_id" : 26, "sum_" : 10000 }
{ "_id" : 22, "sum_" : 6000 }
{ "_id" : 23, "sum_" : 7000 }
> db.people.aggregate([{$group:{"_id":1,sum_:{$min:"$salary"}}}])
{ "_id" : 1, "sum_" : 6000 }
> db.people.aggregate([{$group:{"_id":1,sum_:{$max:"$salary"}}}])
{ "_id" : 1, "sum_" : 12000 }
> db.people.aggregate([{$group:{"_id":"$age",sum_:{$min:1}}}])
{ "_id" : 26, "sum_" : 1 }
{ "_id" : 22, "sum_" : 1 }
{ "_id" : 23, "sum_" : 1 }
> db.people.find()
{ "_id" : ObjectId("61a896540a49d92010a7f90c"), "id" : "001", "age" : 22, "salary" : 6000 }
{ "_id" : ObjectId("61a896640a49d92010a7f90d"), "id" : "002", "age" : 23, "salary" : 7000 }
{ "_id" : ObjectId("61a896740a49d92010a7f90e"), "id" : "003", "age" : 26, "salary" : 10000 }
{ "_id" : ObjectId("61a974dc09bc2e834dc429f3"), "id" : "004", "age" : 26, "salary" : 12000 }
> db.people.aggregate([{$group:{"_id":"我是丑逼",sum_:{$min:"$salary"}}}])
{ "_id" : "我是丑逼", "sum_" : 6000 }
> db.people.aggregate([{$group:{"_id":"我是帅逼",sum_:{$max:"$salary"}}}])
{ "_id" : "我是帅逼", "sum_" : 12000 }
> db.people.aggregate([{$group:{"_id":"我是帅逼",sum_:{$first:"$salary"}}}])
{ "_id" : "我是帅逼", "sum_" : 6000 }

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