MongoDB学习笔记3-Mongo-Shell-常用查询命令

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MongoDB 学习笔记（3）- Mongo Shell 常用查询命令

本文所使用的 MongoDB 版本为 4.0.10

> db.version();
4.0.10

一、find 命令进行简查询 

find(查询条件，返回的字段)，

1. 查询时返回所有字段

db.user.find() –> 查询 user 集合中所有的数据 

> db.user.find()
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086" }
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30 }
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40 }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

db.user.find({“username”:”Mary”} ) –> 列出 username=Mary 的数据 

> db.user.find({"username": "Mary"})
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30 }

db.user.find({“age”:50} ) –> 列出 age = 50 的数据 

> db.user.find({"age":50} )
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

2. 查询时只返回指定几个字段

db.user.find({}, {“username”:1}) –> 列出所有人的 username 字段 

> db.user.find({}, {"username": 1})
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom" }
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary" }
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin" }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart" }

db.user.find({}, {“tel”: 1}) –> 列出所有人的 tel 字段 

> db.user.find({}, {"tel": 1})
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "tel" : "10086" }
{"_id" : ObjectId("5d2f102414077ad0dab139c7") }
{"_id" : ObjectId("5d2f103414077ad0dab139c8") }
{"_id" : ObjectId("5d2f105414077ad0dab139c9") }

db.user.find({} , {“age”: 0} ) –> 除了 age 字段，其他字段都列出来 

> db.user.find({}, {"age": 0})
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "tel" : "10086" }
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary" }
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin" }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart" }

二、常用操作符

1. $lt (<)

查询年龄小于 30 岁的用户 

> db.user.find({"age": { $lt: 30} } )
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086" }

2. $lte (<=)

查询年龄小于等于 30 岁的用户 

> db.user.find({"age": { $lte: 30} } )
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086" }
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30 }

3. $gt (>)

查询年龄大于 30 岁的用户 

> db.user.find({"age": { $gt: 30} } )
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40 }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

4. $gte (>=)

查询年龄大于等于 30 岁的用户 

> db.user.find({"age": { $gte: 30} } )
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30 }
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40 }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

5. $ne (<>)

查询年龄不等于 30 岁的用户 

> db.user.find({"age": { $ne: 30} } )
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086" }
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40 }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

6. $and (AND)

查询年龄大于 10 岁且小于 40 岁的用户 

> db.user.find({ $and: [ { "age": { $lt: 40} }  , {"age": { $gt: 10} } ] } )
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086" }
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30, "tel" : null }

7. $or (OR)

查询年龄小于 20 岁或者大于 40 岁的用户 

> db.user.find({ $or: [ { "age": { $lt: 20} }  , {"age": { $gt:40} } ] } )
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086" }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

8. $in (IN)

查询年龄为 20, 30, 40 岁的用户 

> db.user.find({ "age" : { $in : [20, 30, 40] } } )
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30 }
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40 }

9. $not (NOT)

查询年龄不是 20, 40 岁的用户（$not）

> db.user.find({ "age" : { $not: { $in : [20, 40] } } } )
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086" }
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30 }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

10. $nin (NOT IN)

查询年龄不是 20, 40 岁的用户 

> db.user.find({ "age" : { $nin : [20, 40] } } )
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086" }
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30 }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

11. $mod (取模)

查询年龄对 4 取模余 2 的用户 

> db.user.find({"age" : { $mod : [4, 2] } } )
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30 }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

12. $exists (存在)

$exists 用于判断键是否

给 Mary 添加 tel 字段，值设为 null

> db.user.update({"username": "Mary"}, {$set : { "tel" : null} })
WriteResult({"nMatched" : 1, "nUpserted" : 0, "nModified" : 1})
> db.user.find()
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086" }
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30, "tel" : null }
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40 }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

列出存在 tel 字段的记录 

> db.user.find({"tel" : { $exists : 1}})
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086" }
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30, "tel" : null }

判断值为 null 时要注意：
db.user.find({"friends" : null})
该命令不仅查出值为 null 的记录，friends 键不存在的记录也会被取出来。

> db.user.find({"tel" : null})
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30, "tel" : null }
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40 }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

如果想取出 friends 键存在，并且值为 null 的记录应该这样来取：

> db.user.find({ $and: [ { "tel" : null}, {"tel" : {$exists: 1} } ] } )
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30, "tel" : null }

13. $where

$where : 根据函数返回值来判断是否返回数据

取出 年龄 * 3 + 5 小于 100 用户的 

db.user.find({ $where : function(){return (this.age * 3 + 5 < 100); 
} } );
> db.user.find({ $where : function(){return (this.age * 3 + 5 < 100); } } );
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086" }
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30, "tel" : null }

this 代表当前这个记录。

通过这个 $where 基本可以实现任意类型的查询。不过不到必要时候不要用这个方法，因为它的速度比一般查询要慢很多。

三、使用正则查询

查找名字中含有 “art” 的记录 

> db.user.find({ "username" : /art/} )
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40 }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

查找以名称以 “mar” 开头且不区分大小写的记录 

> db.user.find({"username": /^mar/i} );
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30, "tel" : null }
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40 }

四、查询数组

1. $all：判断某个数组类型字段包含的多个指定值时。

给 user 集合中的用户添加一些朋友，结果如下：

> db.user.find()
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086", "friend" : ["Mary", "Jocker", "Martin", "Kart"] }
{"_id" : ObjectId("5d2f102414077ad0dab139c7"), "username" : "Mary", "age" : 30, "tel" : null, "friend" : ["Jocker", "Martin"] }
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40, "friend" : ["Mary", "Jocker", "Kart"] }
{"_id" : ObjectId("5d2f105414077ad0dab139c9"), "username" : "kart", "age" : 50 }

取出 friend 数组中既有 Mary 又有 Jocker 的记录 

> db.user.find({"friend": { $all : ["Mary", "Jocker"] } })
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086", "friend" : ["Mary", "Jocker", "Martin", "Kart"] }
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40, "friend" : ["Mary", "Jocker", "Kart"] }

2. $size：查询拥有指定元素个数的数组

取出 friend 数组中有 3 个值的记录 

> db.user.find({ "friend" : { $size  : 3} } )
{"_id" : ObjectId("5d2f103414077ad0dab139c8"), "username" : "Martin", "age" : 40, "friend" : ["Mary", "Jocker", "Kart"] }

3. $slice : 返回一个数组的子集

{$slice : 10} –> 数组中的前 10 个
{$slice : -10} –> 数组中的后 10 个
{$slice : [20, 10] } –> 从数组中下标为 20 的元素开始，向后去除 10 个元素

取出 Tom 的前 3 个朋友 

> db.user.find({"username": "Tom"}, {"friend" : {$slice : 3} } )
{"_id" : ObjectId("5d2f0a4714077ad0dab139c5"), "username" : "Tom", "age" : 12, "tel" : "10086", "friend" : ["Mary", "Jocker", "Martin"] }

五、查询内嵌文档

1. $elemMatch

如有这样的数据结构：
有个 comments 字段，该字段是一个数组，每一项是一个内嵌的 comment 对象 

{"_id": ObjectId("5d31b1d24fd0d7ad0a1a1361"),
    "author": "Tom",
    "content": "I am Tom!",
    "comments": [{
        "user": "Mary",
        "score": 3,
        "comment": "Nice!"
    }, {
        "user": "Martin",
        "score": 6,
        "comment": "I'm reading..."}, {"user":"Jocker","score": 8,"comment":"You're kidding me"}]
}
{"_id": ObjectId("5d31b3114fd0d7ad0a1a1364"),
    "author": "Martin",
    "content": "I am Martin!",
    "comments": [{
        "user": "Tom",
        "score": 5,
        "comment": "Nice!"
    }, {
        "user": "Mary",
        "score": 6,
        "comment": "I'm reading..."}, {"user":"Jocker","score": 3,"comment":"You're kidding me"}]
}
{"_id": ObjectId("5d31b3314fd0d7ad0a1a1365"),
    "author": "Mary",
    "content": "I am Mary!",
    "comments": [{
        "user": "Tom",
        "score": 3,
        "comment": "Nice!"
    }, {
        "user": "Martin",
        "score": 5,
        "comment": "I'm reading..."}, {"user":"Jocker","score": 2,"comment":"You're kidding me"}]
}

查询评论中包含 score 大于 5 的文章记录 

> db.blog.find ({"comments" : { "$elemMatch" : { "score" : {"$gt" : 5}}} })
{"_id" : ObjectId("5d31b1d24fd0d7ad0a1a1361"), "author" : "Tom", "content" : "I am Tom!", "comments" : [{ "user" : "Mary", "score" : 3, "comment" : "Nice!"}, {"user" : "Martin", "score" : 6, "comment" : "I'm reading..."}, {"user":"Jocker","score": 8,"comment":"You're kidding me"} ] }
{"_id" : ObjectId("5d31b3114fd0d7ad0a1a1364"), "author" : "Martin", "content" : "I am Martin!", "comments" : [{ "user" : "Tom", "score" : 5, "comment" : "Nice!"}, {"user" : "Mary", "score" : 6, "comment" : "I'm reading..."}, {"user":"Jocker","score": 3,"comment":"You're kidding me"} ] }

查询 Tom 的文章的评论中 score 大于 5 的评论记录 

> db.blog.find ({"author": "Tom"}, {"comments" : { "$elemMatch" : { "score" : {"$gt" : 3}}} })
{"_id" : ObjectId("5d31b1d24fd0d7ad0a1a1361"), "comments" : [{ "user" : "Martin", "score" : 6, "comment" : "I'm reading..."} ] }

正文完
mongodb node.js nosql php
发表至： javascript
2019-07-30
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