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社区首页 >专栏 >浅尝辄止MongoDB：操作（1）

浅尝辄止MongoDB：操作（1）

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用户1148526
发布于 2019-05-25 19:43:02
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发布于 2019-05-25 19:43:02
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文章被收录于专栏：Hadoop数据仓库Hadoop数据仓库

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://cloud.tencent.com/developer/article/1433171

目录

1. 浏览数据库

2. 插入数据

3. 查询数据

代码语言：txt
复制
    大部分摘自《MongoDB大数据处理权威指南》（第3版）。

1. 浏览数据库

代码语言：txt
复制
    MongoDB在第一次存储数据时会自动创建数据库和集合。要切换到已有数据库或者创建新的数据库，可使用use函数，在命令后加上数据库名，无论它是否存在：
代码语言：javascript
复制
> use library;
switched to db library
> db
library
>
代码语言：txt
复制
    通过这种方式将全局变量db设置为library。这意味着，接下来的所有输入到MongoDB shell中的命令都将在library中执行，除非将该变量重置为另一个数据库。
代码语言：txt
复制
    查看可用数据库：
代码语言：javascript
复制
> show dbs;
admin   0.000GB
config  0.000GB
local   0.000GB
>
代码语言：txt
复制
    在向library库存储数据前，show dbs命令不返回library库。
代码语言：txt
复制
    查看当前数据库：
代码语言：javascript
复制
> db.getName();
library
> db
library
>
代码语言：txt
复制
    查看当前数据库中的集合：
代码语言：javascript
复制
> show collections;
>

2. 插入数据

代码语言：txt
复制
    插入数据使用BSON格式。
代码语言：javascript
复制
> document = ({"Type": "Book", "Title" : "Definitive Guide to MongoDB 3rd ed., The",
... "ISBN" : "978-1-4842-1183-0", "Publisher" : "Apress", 
... "Author" : ["Hows, David", "Plugge, Eelco", "Membrey, Peter", "Hawkins, Tim"] } );
{
    "Type" : "Book",
    "Title" : "Definitive Guide to MongoDB 3rd ed., The",
    "ISBN" : "978-1-4842-1183-0",
    "Publisher" : "Apress",
    "Author" : [
        "Hows, David",
        "Plugge, Eelco",
        "Membrey, Peter",
        "Hawkins, Tim"
    ]
}
> db.media.insert(document);
WriteResult({ "nInserted" : 1 })
> db.media.insertOne(document);
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5baae32864e6602b766d94c1")
}
>
代码语言：txt
复制
    insert和insertOne函数的返回值不同。insert插入单条返回WriteResult对象，插入多条返回BulkWriteResult对象。而insertOne插入单条返回文档ID，insertMany插入多条返回多个文档ID构成的数组。
代码语言：javascript
复制
> document = ( { "Type" : "Book",
... "Title" : "Definitive Guide to MongoDB 3rd ed., The",
... "ISBN" : " 978-1-4842-1183-0",
... "Publisher" : "Apress",
... "Author" : ["Hows, David", "Plugge, Eelco", "Membrey, Peter", "Hawkins, Tim"]
... } );
{
    "Type" : "Book",
    "Title" : "Definitive Guide to MongoDB 3rd ed., The",
    "ISBN" : " 978-1-4842-1183-0",
    "Publisher" : "Apress",
    "Author" : [
        "Hows, David",
        "Plugge, Eelco",
        "Membrey, Peter",
        "Hawkins, Tim"
    ]
}
> db.media.insert(document);
WriteResult({ "nInserted" : 1 })
> db.media.insertOne( { "Type" : "CD", "Artist" : "Nirvana", "Title" : "Nevermind" });
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5baae67464e6602b766d94c3")
}
> db.media.insertOne( { "Type" : "CD",
... "Artist" : "Nirvana",
... "Title" : "Nevermind",
...  "Tracklist" : [
...  {
...  "Track" : "1",
...  "Title" : "Smells Like Teen Spirit",
...  "Length" : "5:02"
...  },
...  {
...  "Track" : "2",
...  "Title" : "In Bloom",
...  "Length" : "4:15"
...  }
...  ]
... }
... );
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5baae6bb64e6602b766d94c4")
}
> db.products.insertMany( [
...       { _id: 10, item: "large box", qty: 20 },
...       { _id: 11, item: "small box", qty: 55 },
...       { _id: 12, item: "medium box", qty: 30 }
...    ] );
{ "acknowledged" : true, "insertedIds" : [ 10, 11, 12 ] }
>  db.products.insertMany( [
...       { item: "large box", qty: 20 },
...       { item: "small box", qty: 55 },
...       { item: "medium box", qty: 30 }
...    ] );
{
    "acknowledged" : true,
    "insertedIds" : [
        ObjectId("5baae89e64e6602b766d94c5"),
        ObjectId("5baae89e64e6602b766d94c6"),
        ObjectId("5baae89e64e6602b766d94c7")
    ]
}
>
代码语言：txt
复制
    在插入文档时，键名必须遵守如下规则：
  • $不能是键名的第一个字符。
  • 圆点.不能出现在键名中。
  • 名称_id被保留用作主键ID，但可以保存任何唯一值。

3. 查询数据

代码语言：txt
复制
    查询全部数据：
代码语言：javascript
复制
db.media.find();
-- 对比SQL：
select * from media;
代码语言：txt
复制
    查询Artist = 'Nirvana'的数据：
代码语言：javascript
复制
db.media.find({ Artist : "Nirvana" });
-- 对比SQL：
select * from media where Artist = 'Nirvana';
代码语言：txt
复制
    查询Artist = 'Nirvana'的Title：
代码语言：javascript
复制
db.media.find ( {Artist : "Nirvana"}, {Title: 1} )
-- 对比SQL：
select Title from media where Artist = 'Nirvana';
代码语言：txt
复制
    查询Artist = 'Nirvana' and Type = 'CD'的Title和Tracklist：
代码语言：javascript
复制
db.media.find ( {Artist : "Nirvana", Type : "CD"}, {Title: 1, Tracklist : 1} );
-- 对比SQL：
select Title, Tracklist from media where Artist = 'Nirvana' and Type = 'CD';

（1）使用点号

代码语言：txt
复制
     嵌入式对象的元素引用：
代码语言：javascript
复制
db.media.find( { "Tracklist.Title" : "In Bloom" } )
-- 对比SQL：
select * from media where Tracklist.Title = 'In Bloom';
代码语言：txt
复制
    数组元素引用：
代码语言：javascript
复制
db.media.find( { "Author" : "Membrey, Peter" } );
-- 对比SQL：
select * from media where 'Membrey, Peter' in Author;
代码语言：txt
复制
    子对象必须精确匹配到最下一级，下面的命令不返回结果：
代码语言：javascript
复制
db.media.find( { "Tracklist" : {"Track" : "1" }} );
代码语言：txt
复制
    正确的写法为：
代码语言：javascript
复制
db.media.find( { "Tracklist.Track" : "1" } );

（2）使用sort、limit和skip

代码语言：txt
复制
     查询结果按Title正序：
代码语言：javascript
复制
db.media.find().sort( { Title: 1 });
-- 对比SQL：
select * from media order by Title asc;
代码语言：txt
复制
    返回2条记录：
代码语言：javascript
复制
db.media.find().limit( 2 );
-- 对比SQL：
select * from media limit 2;
代码语言：txt
复制
    查询结果按Title倒序返回2条：
代码语言：javascript
复制
db.media.find().sort( { Title: -1 }).limit( 2 );
-- 对比SQL：
select * from media order by Title desc limit 2;
代码语言：txt
复制
    查询结果跳过1前20条：
代码语言：javascript
复制
db.media.find().skip(20);
-- 对比SQL：
select * from media limit 21, 999999999999999;
代码语言：txt
复制
    查询结果按Title倒序，返回从21条开始的10条数据：
代码语言：javascript
复制
db.media.find().sort ( { Title : -1 } ).limit ( 10 ).skip ( 20 )
-- 对比SQL：
select * from media order by Title desc limit 20, 10;
代码语言：txt
复制
    skip和limit，当两者一起使用的时候，不管其位置顺序，默认先skip，再limit。当sort、skip、limit一起使用时，无论其位置变化，总是先sort再skip，最后limit。
代码语言：txt
复制
    db.media.find().limit(2).skip(2)的快捷写法：
代码语言：javascript
复制
db.media.find({},{}, 2, 2 );

（3）使用固定集合

代码语言：txt
复制
     固定集合具有以下性质：
  • 固定集合（capped collection）是数据库的一种集合，它的自然顺序保证与文档插入的顺序一致。这点在需要将查询的结果严格按照文档插入顺序时非常有用。
  • 固定集合的大小固定。一旦固定集合达到设置的大小，最老的数据将被删除，最新的数据将被添加到末端，保证自然顺序与文档插入的顺序一致。该类型的集合可用于日志或自动归档数据。
  • 与标准集合不同，固定集合必须使用createCollection函数，以显式方式创建。必须使用参数指定集合的大小（单位为字节）。
  • 已经添加到固定集合的文档可以更新，但文档大小不能改变，否则更新将会失败。也不能从固定集合中删除文档。如果要删除文档，必须删除整个集合并重建。
代码语言：txt
复制
    创建一个固定集合，没有数据时也会在show collections中返回。
代码语言：javascript
复制
> db.createCollection("audit", {capped:true, size:20480});
{ "ok" : 1 }
> show collections;
audit
media
products
> db.audit.insertMany([{item: "large box", qty: 20},{item: "small box", qty: 55},{item: "medium box", qty: 30}]);
{
    "acknowledged" : true,
    "insertedIds" : [
        ObjectId("5bab1d6c1062c31f5bdf6645"),
        ObjectId("5bab1d6c1062c31f5bdf6646"),
        ObjectId("5bab1d6c1062c31f5bdf6647")
    ]
}
>
代码语言：txt
复制
    鉴于固定集合保证了自然顺序与插入顺序一致，那么在查询数据时，就不需要再使用任何特殊的参数、任何其它特殊的命令或函数，除非希望逆转默认结果的顺序。这时将用到$natural参数。
代码语言：javascript
复制
> db.audit.find();
{ "_id" : ObjectId("5bab1d6c1062c31f5bdf6645"), "item" : "large box", "qty" : 20 }
{ "_id" : ObjectId("5bab1d6c1062c31f5bdf6646"), "item" : "small box", "qty" : 55 }
{ "_id" : ObjectId("5bab1d6c1062c31f5bdf6647"), "item" : "medium box", "qty" : 30 }
> db.audit.find().sort( { $natural: -1 } ).limit(10);
{ "_id" : ObjectId("5bab1d6c1062c31f5bdf6647"), "item" : "medium box", "qty" : 30 }
{ "_id" : ObjectId("5bab1d6c1062c31f5bdf6646"), "item" : "small box", "qty" : 55 }
{ "_id" : ObjectId("5bab1d6c1062c31f5bdf6645"), "item" : "large box", "qty" : 20 }
>
代码语言：txt
复制
    还可以使用max:参数限制添加到固定集合中的文档数量，创建集合时使用该参数。
代码语言：javascript
复制
> db.createCollection("audit100", { capped:true, size:20480, max: 100});
{ "ok" : 1 }
> db.audit100.stats()
{
    "ns" : "library.audit100",
    "size" : 0,
    "count" : 0,
    "storageSize" : 4096,
    "capped" : true,
    "max" : 100,
    "maxSize" : 20480,
    "sleepCount" : 0,
    "sleepMS" : 0,
    "wiredTiger" : {
       ...
    },
    "nindexes" : 1,
    "totalIndexSize" : 4096,
    "indexSizes" : {
        "_id_" : 4096
    },
    "ok" : 1
}
>

（4）获取单个文档

代码语言：javascript
复制
> db.media.findOne();
{
    "_id" : ObjectId("5baae32464e6602b766d94c0"),
    "Type" : "Book",
    "Title" : "Definitive Guide to MongoDB 3rd ed., The",
    "ISBN" : "978-1-4842-1183-0",
    "Publisher" : "Apress",
    "Author" : [
        "Hows, David",
        "Plugge, Eelco",
        "Membrey, Peter",
        "Hawkins, Tim"
    ]
}
>
代码语言：txt
复制
    如果希望返回一个结果，建议使用findOne()函数。

（5）使用聚合命令

  • count()
代码语言：javascript
复制
db.media.count();
-- 对比SQL：
select count(*) from media;

db.media.find( { Publisher : "Apress", Type: "Book" } ).count();
-- 对比SQL：
select count(*) from media where Publisher = 'Apress' and Type = 'Book';
代码语言：txt
复制
    count()函数默认忽略skip()或limit()函数，为确保查询不忽略这些参数，使用count(true)：
代码语言：javascript
复制
> db.media.find( { Publisher: "Apress", Type: "Book" }).skip(10).count();
3
> db.media.find( { Publisher: "Apress", Type: "Book" }).skip(10).count(true);
0
>
  • distinct()
代码语言：txt
复制
    先插入一条数据：
代码语言：javascript
复制
> document = ( { "Type" : "Book", "Title" : "Definitive Guide to MongoDB 3rd ed., The", ISBN:
... " 978-1-4842-1183-1", "Publisher" : "Apress", "Author" : ["Hows, David", "Membrey, Peter",
... "Plugge, Eelco", "Hawkins, Tim"] } );
{
    "Type" : "Book",
    "Title" : "Definitive Guide to MongoDB 3rd ed., The",
    "ISBN" : " 978-1-4842-1183-1",
    "Publisher" : "Apress",
    "Author" : [
        "Hows, David",
        "Membrey, Peter",
        "Plugge, Eelco",
        "Hawkins, Tim"
    ]
}
> db.media.insert (document);
WriteResult({ "nInserted" : 1 })
>
代码语言：txt
复制
    distinct返回去重后的结果：
代码语言：javascript
复制
> db.media.distinct( "Title");
[ "Definitive Guide to MongoDB 3rd ed., The", "Nevermind" ]
> db.media.distinct ("ISBN");
[ "978-1-4842-1183-0", " 978-1-4842-1183-0", " 978-1-4842-1183-1" ]
> db.media.distinct ("Tracklist.Title");
[ "In Bloom", "Smells Like Teen Spirit" ]
>
  • group()
代码语言：txt
复制
    函数group()接受3个参数：key、initial和reduce。key是分组键，initial是聚合初始值（基数），reduce定义聚合函数。
代码语言：javascript
复制
> db.media.group (
... {
... key: {Title : true},
... initial: {Total : 0},
... reduce : function (items,prev)
... {
... prev.Total += 1
... }
... }
... );
[
    {
        "Title" : "Definitive Guide to MongoDB 3rd ed., The",
        "Total" : 4
    },
    {
        "Title" : "Nevermind",
        "Total" : 2
    }
]
>
-- 对比SQL： 
select Title, count(*) from media group by Title;

函数group()目前在分片环境中无法正常工作。因此在这种环境中应该使用mapreduce()。另外group()函数输出结果中的键不能超过20000个，否则将抛出异常。此类情况也可以通过mapreduce()处理。

（6）使用条件操作符

代码语言：txt
复制
     添加一些文档：
代码语言：javascript
复制
> dvd = ( { "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999,
... "Cast" : ["Keanu Reeves","Carrie-Anne Moss","Laurence Fishburne","Hugo Weaving","Gloria Foster","Joe Pantoliano"] } );
{
    "Type" : "DVD",
    "Title" : "Matrix, The",
    "Released" : 1999,
    "Cast" : [
        "Keanu Reeves",
        "Carrie-Anne Moss",
        "Laurence Fishburne",
        "Hugo Weaving",
        "Gloria Foster",
        "Joe Pantoliano"
    ]
}
> db.media.insertOne(dvd);
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5bab30251062c31f5bdf6649")
}
> dvd = ( { "Type" : "DVD", Title : "Blade Runner", Released : 1982 } );
{ "Type" : "DVD", "Title" : "Blade Runner", "Released" : 1982 }
> db.media.insertOne(dvd);
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5bab303e1062c31f5bdf664a")
}
> dvd = ( { "Type" : "DVD", Title : "Toy Story 3", Released : 2010 } );
{ "Type" : "DVD", "Title" : "Toy Story 3", "Released" : 2010 }
> db.media.insertOne(dvd);
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5bab30521062c31f5bdf664b")
}
>
  • 大于、小于比较
代码语言：javascript
复制
> db.media.find ( { Released : {$gt : 2000} }, { "Cast" : 0 } );
{ "_id" : ObjectId("5bab30521062c31f5bdf664b"), "Type" : "DVD", "Title" : "Toy Story 3", "Released" : 2010 }
> 
-- 对比SQL：
select Type, Title, Released from media where Released > 2000;

> db.media.find ( { Released : {$gte : 1999 } }, { "Cast" : 0 } );
{ "_id" : ObjectId("5bab30251062c31f5bdf6649"), "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999 }
{ "_id" : ObjectId("5bab30521062c31f5bdf664b"), "Type" : "DVD", "Title" : "Toy Story 3", "Released" : 2010 }
> 
-- 对比SQL：
select Type, Title, Released from media where Released >= 1999;

> db.media.find ( { Released : {$lt : 1999 } }, { "Cast" : 0 } );
{ "_id" : ObjectId("5bab303e1062c31f5bdf664a"), "Type" : "DVD", "Title" : "Blade Runner", "Released" : 1982 }
>
-- 对比SQL：
select Type, Title, Released from media where Released < 1999;

> db.media.find( {Released : {$lte: 1999}}, { "Cast" : 0 });
{ "_id" : ObjectId("5bab30251062c31f5bdf6649"), "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999 }
{ "_id" : ObjectId("5bab303e1062c31f5bdf664a"), "Type" : "DVD", "Title" : "Blade Runner", "Released" : 1982 }
> 
-- 对比SQL：
select Type, Title, Released from media where Released <= 1999;

> db.media.find( {Released : {$gte: 1990, $lt : 2010}}, { "Cast" : 0 });
{ "_id" : ObjectId("5bab30251062c31f5bdf6649"), "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999 }
> 
-- 对比SQL：
select Type, Title, Released from media where Released >= 1990 and Released < 2010;
  • 不等于
代码语言：javascript
复制
> db.media.find( { Type : "Book", Author: {$ne : "Plugge, Eelco"}});
>
-- 对比SQL：
select * from media where Type = 'Book' and 'Plugge, Eelco' not in Author;
  • $in
代码语言：javascript
复制
> db.media.find( {Released : {$in : [1999,2008,2009] } }, { "Cast" : 0 } );
{ "_id" : ObjectId("5bab30251062c31f5bdf6649"), "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999 }
>
-- 对比SQL：
select Type, Title, Released from media where Released in (1999, 2008, 2009);
  • $nin
代码语言：javascript
复制
> db.media.find( {Released : {$nin : [1999,2008,2009] },Type : "DVD" }, { "Cast" : 0 } );
{ "_id" : ObjectId("5bab303e1062c31f5bdf664a"), "Type" : "DVD", "Title" : "Blade Runner", "Released" : 1982 }
{ "_id" : ObjectId("5bab30521062c31f5bdf664b"), "Type" : "DVD", "Title" : "Toy Story 3", "Released" : 2010 }
>
-- 对比SQL：
select Type, Title, Released from media where Released not in (1999, 2008, 2009);
  • $all
代码语言：javascript
复制
> db.media.find ( { Released : {$in : [2010,2009] } }, { "Cast" : 0 } );
{ "_id" : ObjectId("5bab30521062c31f5bdf664b"), "Type" : "DVD", "Title" : "Toy Story 3", "Released" : 2010 }
> db.media.find ( { Released : {$all : [2010,2009] } }, { "Cast" : 0 } );
>
-- 对比SQL：
select Type, Title, Released from media where Released = '2010,2009';
  • $or
代码语言：javascript
复制
> db.media.find({ $or : [ { "Title" : "Toy Story 3" }, { "ISBN" : "978-1-4842-1183-0" } ] } );
{ "_id" : ObjectId("5baae32464e6602b766d94c0"), "Type" : "Book", "Title" : "Definitive Guide to MongoDB 3rd ed., The", "ISBN" : "978-1-4842-1183-0", "Publisher" : "Apress", "Author" : [ "Hows, David", "Plugge, Eelco", "Membrey, Peter", "Hawkins, Tim" ] }
{ "_id" : ObjectId("5baae32864e6602b766d94c1"), "Type" : "Book", "Title" : "Definitive Guide to MongoDB 3rd ed., The", "ISBN" : "978-1-4842-1183-0", "Publisher" : "Apress", "Author" : [ "Hows, David", "Plugge, Eelco", "Membrey, Peter", "Hawkins, Tim" ] }
{ "_id" : ObjectId("5bab30521062c31f5bdf664b"), "Type" : "DVD", "Title" : "Toy Story 3", "Released" : 2010 }
> 
-- 对比SQL：
select * from media where Title = 'Toy Story 3' or ISBN = '978-1-4842-1183-0';

> db.media.find({ "Type" : "DVD", $or : [ { "Title" : "Toy Story 3" },
... { "ISBN" : "978-1-4842-1183-0" } ] });
{ "_id" : ObjectId("5bab30521062c31f5bdf664b"), "Type" : "DVD", "Title" : "Toy Story 3", "Released" : 2010 }
>
-- 对比SQL：
select * from media where Type = 'DVD' and (Title = 'Toy Story 3' or ISBN = '978-1-4842-1183-0');
  • $slice（数组子集）
代码语言：javascript
复制
> db.media.find({"Title" : "Matrix, The"}, {"Cast" : {$slice: 3}});
{ "_id" : ObjectId("5bab30251062c31f5bdf6649"), "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999, "Cast" : [ "Keanu Reeves", "Carrie-Anne Moss", "Laurence Fishburne" ] }
> 
-- 对比SQL：
select Type, Title, Released, substring_index(Cast,',',3) from media where Title = 'Matrix, The';

> db.media.find({"Title" : "Matrix, The"}, {"Cast" : {$slice: -3}});
{ "_id" : ObjectId("5bab30251062c31f5bdf6649"), "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999, "Cast" : [ "Hugo Weaving", "Gloria Foster", "Joe Pantoliano" ] }
>
-- 对比SQL：
select Type, Title, Released, substring_index(Cast,',',-3) from media where Title = 'Matrix, The';

> db.media.find({"Title" : "Matrix, The"}, {"Cast" : {$slice: [2,3] }});
{ "_id" : ObjectId("5bab30251062c31f5bdf6649"), "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999, "Cast" : [ "Laurence Fishburne", "Hugo Weaving", "Gloria Foster" ] }
>
-- 对比SQL：
select Type, Title, Released, 
       substring_index(substring_index(@Cast,',',1-(length(Cast)-length(replace(Cast,',','')))),',',3)
  from media where Title = 'Matrix, The';

> db.media.find({"Title" : "Matrix, The"}, {"Cast" : {$slice: [-5,4] }});
{ "_id" : ObjectId("5bab30251062c31f5bdf6649"), "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999, "Cast" : [ "Carrie-Anne Moss", "Laurence Fishburne", "Hugo Weaving", "Gloria Foster" ] }
>
-- 对比SQL：
select Type, Title, Released, 
       substring_index(substring_index(@Cast,',',-(length(Cast)-length(replace(Cast,',','')))),',',4)
  from media where Title = 'Matrix, The';
  • $mod
代码语言：javascript
复制
> db.media.find ( { Released : { $mod: [2,0] } }, {"Cast" : 0 } );
{ "_id" : ObjectId("5bab303e1062c31f5bdf664a"), "Type" : "DVD", "Title" : "Blade Runner", "Released" : 1982 }
{ "_id" : ObjectId("5bab30521062c31f5bdf664b"), "Type" : "DVD", "Title" : "Toy Story 3", "Released" : 2010 }
>
-- 对比SQL：
select Type, Title, Released from media where mod(Released,2) = 0;

> db.media.find ( { Released : { $mod: [2,1] } }, { "Cast" : 0 } );
{ "_id" : ObjectId("5bab30251062c31f5bdf6649"), "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999 }
> 
-- 对比SQL：
select Type, Title, Released from media where mod(Released,2) = 1;
  • $size（数组元素个数）
代码语言：javascript
复制
> db.media.find ( { Tracklist : {$size : 2} } );
{ "_id" : ObjectId("5baae6bb64e6602b766d94c4"), "Type" : "CD", "Artist" : "Nirvana", "Title" : "Nevermind", "Tracklist" : [ { "Track" : "1", "Title" : "Smells Like Teen Spirit", "Length" : "5:02" }, { "Track" : "2", "Title" : "In Bloom", "Length" : "4:15" } ] }
>
-- 对比SQL：
select * from media where length(Tracklist)-length(replace(Tracklist,',','')) = 2;
  • $exists（判断键是否存在）
代码语言：javascript
复制
> db.media.find ( { Author : {$exists : true } } );
{ "_id" : ObjectId("5baae32464e6602b766d94c0"), "Type" : "Book", "Title" : "Definitive Guide to MongoDB 3rd ed., The", "ISBN" : "978-1-4842-1183-0", "Publisher" : "Apress", "Author" : [ "Hows, David", "Plugge, Eelco", "Membrey, Peter", "Hawkins, Tim" ] }
{ "_id" : ObjectId("5baae32864e6602b766d94c1"), "Type" : "Book", "Title" : "Definitive Guide to MongoDB 3rd ed., The", "ISBN" : "978-1-4842-1183-0", "Publisher" : "Apress", "Author" : [ "Hows, David", "Plugge, Eelco", "Membrey, Peter", "Hawkins, Tim" ] }
{ "_id" : ObjectId("5baae64864e6602b766d94c2"), "Type" : "Book", "Title" : "Definitive Guide to MongoDB 3rd ed., The", "ISBN" : " 978-1-4842-1183-0", "Publisher" : "Apress", "Author" : [ "Hows, David", "Plugge, Eelco", "Membrey, Peter", "Hawkins, Tim" ] }
{ "_id" : ObjectId("5bab22551062c31f5bdf6648"), "Type" : "Book", "Title" : "Definitive Guide to MongoDB 3rd ed., The", "ISBN" : " 978-1-4842-1183-1", "Publisher" : "Apress", "Author" : [ "Hows, David", "Membrey, Peter", "Plugge, Eelco", "Hawkins, Tim" ] }
> 
> db.media.find ( { Author : {$exists : false } } );
{ "_id" : ObjectId("5baae67464e6602b766d94c3"), "Type" : "CD", "Artist" : "Nirvana", "Title" : "Nevermind" }
{ "_id" : ObjectId("5baae6bb64e6602b766d94c4"), "Type" : "CD", "Artist" : "Nirvana", "Title" : "Nevermind", "Tracklist" : [ { "Track" : "1", "Title" : "Smells Like Teen Spirit", "Length" : "5:02" }, { "Track" : "2", "Title" : "In Bloom", "Length" : "4:15" } ] }
{ "_id" : ObjectId("5bab30251062c31f5bdf6649"), "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999, "Cast" : [ "Keanu Reeves", "Carrie-Anne Moss", "Laurence Fishburne", "Hugo Weaving", "Gloria Foster", "Joe Pantoliano" ] }
{ "_id" : ObjectId("5bab303e1062c31f5bdf664a"), "Type" : "DVD", "Title" : "Blade Runner", "Released" : 1982 }
{ "_id" : ObjectId("5bab30521062c31f5bdf664b"), "Type" : "DVD", "Title" : "Toy Story 3", "Released" : 2010 }
>
  • $type（基于BSON类型匹配结果）
代码语言：javascript
复制
> db.media.find ( { Tracklist: { $type : 3 } } );
{ "_id" : ObjectId("5baae6bb64e6602b766d94c4"), "Type" : "CD", "Artist" : "Nirvana", "Title" : "Nevermind", "Tracklist" : [ { "Track" : "1", "Title" : "Smells Like Teen Spirit", "Length" : "5:02" }, { "Track" : "2", "Title" : "In Bloom", "Length" : "4:15" } ] }
>
代码语言：txt
复制
    BSON数据类型和代码如下表：

代码

数据类型

-1

MiniKey

1

Double

2

Character字符串（UTF8）

3

嵌入式对象

4

嵌入式数组

5

二进制数据

7

对象ID

8

Boolean

9

Date

10

Null

11

正则表达式

13

JavaScript代码

14

Symbol

15

带作用域的JavaScript代码

16

32位整数

17

时间戳

18

64位整数

127

MaxKey

255

MinKey

  • $elemMatch（匹配完整的数组）
代码语言：txt
复制
    添加一条数据：
代码语言：javascript
复制
> nirvana = ( { "Type" : "CD", "Artist" : "Nirvana", "Title" : "Nirvana", "Tracklist" :
... [ { "Track" : "1", "Title" : "You Know You're Right", "Length" : "3:38"}, {"Track" : "5",
... "Title" : "Smells Like Teen Spirit", "Length" : "5:02" } ] } );
{
    "Type" : "CD",
    "Artist" : "Nirvana",
    "Title" : "Nirvana",
    "Tracklist" : [
        {
            "Track" : "1",
            "Title" : "You Know You're Right",
            "Length" : "3:38"
        },
        {
            "Track" : "5",
            "Title" : "Smells Like Teen Spirit",
            "Length" : "5:02"
        }
    ]
}
> db.media.insertOne(nirvana);
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5bac38628acb19ced2e28ed4")
}
>
代码语言：txt
复制
    下面查询返回Tracklist.Title = "Smells Like Teen Spirit" or Tracklist.Track = "1"的数据：
代码语言：javascript
复制
> db.media.find ( { "Tracklist.Title" : "Smells Like Teen Spirit", "Tracklist.Track" : "1" } );
{ "_id" : ObjectId("5baae6bb64e6602b766d94c4"), "Type" : "CD", "Artist" : "Nirvana", "Title" : "Nevermind", "Tracklist" : [ { "Track" : "1", "Title" : "Smells Like Teen Spirit", "Length" : "5:02" }, { "Track" : "2", "Title" : "In Bloom", "Length" : "4:15" } ] }
{ "_id" : ObjectId("5bac38628acb19ced2e28ed4"), "Type" : "CD", "Artist" : "Nirvana", "Title" : "Nirvana", "Tracklist" : [ { "Track" : "1", "Title" : "You Know You're Right", "Length" : "3:38" }, { "Track" : "5", "Title" : "Smells Like Teen Spirit", "Length" : "5:02" } ] }
> 
-- 对比SQL：
select * from media where Tracklist.Title = 'Smells Like Teen Spirit' or Tracklist.Track = "1";
代码语言：txt
复制
    用$elemMatch匹配数组中的完整元素：
代码语言：javascript
复制
> db.media.find ( { Tracklist: { "$elemMatch" : { Title: "Smells Like Teen Spirit",
... Track : "1" } } } );
{ "_id" : ObjectId("5baae6bb64e6602b766d94c4"), "Type" : "CD", "Artist" : "Nirvana", "Title" : "Nevermind", "Tracklist" : [ { "Track" : "1", "Title" : "Smells Like Teen Spirit", "Length" : "5:02" }, { "Track" : "2", "Title" : "In Bloom", "Length" : "4:15" } ] }
>
-- 对比SQL：
select * from media where Tracklist.Title = 'Smells Like Teen Spirit' and Tracklist.Track = "1";
  • $not元操作符
代码语言：txt
复制
    查询集合中除了$elemMatch匹配的所有文档：
代码语言：javascript
复制
db.media.find ( { Tracklist : { $not : { "$elemMatch" : { Title: "Smells Like Teen Spirit", "Track" : "1" } } } } );
-- 对比SQL：
select * from media where not (Tracklist.Title = 'Smells Like Teen Spirit' and Tracklist.Track = "1");
  • 指定额外的查询表达式
代码语言：txt
复制
    可以使用JavaScript指定额外的查询表达式。这种方式的优势在于JavaScript非常灵活，并且允许执行大量的额外查询。缺点是它比MongoDB支持的原生操作符慢一点，因为它不能使用索引。下面的查询都返回同样的结果：
代码语言：javascript
复制
db.media.find ( { "Type" : "DVD", "Released" : { $lt : 1995 } } )

db.media.find ( { "Type" : "DVD", $where: "this.Released < 1995" } )

db.media.find ("this.Released < 1995")

f = function() { return this.Released < 1995 }
db.media.find(f)

（7）使用正则表达式

代码语言：txt
复制
     查询Title以'Matrix'（不区分大小写）开头的数据：
代码语言：javascript
复制
> db.media.find ( { Title : /^Matrix/ } );
{ "_id" : ObjectId("5bab30251062c31f5bdf6649"), "Type" : "DVD", "Title" : "Matrix, The", "Released" : 1999, "Cast" : [ "Keanu Reeves", "Carrie-Anne Moss", "Laurence Fishburne", "Hugo Weaving", "Gloria Foster", "Joe Pantoliano" ] }
>
-- 对比SQL：
select * from media where Title regexp '^Matrix';
代码语言：txt
复制
    注意，不分大小写（“i”）的正则表达式查询性能不好，因为需要执行大量搜索。
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原始发表：2018年09月27日，如有侵权请联系 cloudcommunity@tencent.com 删除
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  • 1. 浏览数据库
  • 2. 插入数据
  • 3. 查询数据
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